[usb] Remove unnecessary complete_cb and cookie initializations

With usb request having private regions for each layer in the stack,
the complete callback and their contexts should not be part of the public
part of the usb-request. In previous changes, I have made the complete_cb
and the cookie as parameters. This changeset removes the unnecessary
initializations of these fields. Once all the usage has been removed, I
will remove these fields from the struct.

Test:
Astro: netboot. lsusb.
Pixelbook: fx serve. fx shell. lsusb. bt cli. list adapters.discoverable

Change-Id: I515a9500be75a8b7bd9b67cba4c64534d5372913
diff --git a/drivers/bluetooth/hci/atheros/device.cpp b/drivers/bluetooth/hci/atheros/device.cpp
index 6e801c5..c313195 100644
--- a/drivers/bluetooth/hci/atheros/device.cpp
+++ b/drivers/bluetooth/hci/atheros/device.cpp
@@ -107,8 +107,6 @@
     req->size = size;
     req->header.length = size;
     usb_request_copy_to(req, file.view(sent, size).data(), size, 0);
-    req->complete_cb = interrupt_complete;
-    req->cookie = &completion_;
     sync_completion_reset(&completion_);
     usb_request_queue(&usb_, req, interrupt_compelete, &completion_);
     sync_completion_wait(&completion_, ZX_TIME_INFINITE);
@@ -162,8 +160,6 @@
     req->size = size;
     req->header.length = size;
     usb_request_copy_to(req, file.view(sent, size).data(), size, 0);
-    req->complete_cb = interrupt_complete;
-    req->cookie = &completion_;
     sync_completion_reset(&completion_);
     usb_request_queue(&usb_, req, interrupt_complete, &completion_);
     sync_completion_wait(&completion_, ZX_TIME_INFINITE);
diff --git a/drivers/telephony/qmi-usb-transport/qmi-usb-transport.c b/drivers/telephony/qmi-usb-transport/qmi-usb-transport.c
index 49f3475..8bc5b77 100644
--- a/drivers/telephony/qmi-usb-transport/qmi-usb-transport.c
+++ b/drivers/telephony/qmi-usb-transport/qmi-usb-transport.c
@@ -735,8 +735,6 @@
            zx_status_get_string(status));
     goto fail;
   }
-  int_buf->complete_cb = qmi_interrupt_cb;
-  int_buf->cookie = qmi_ctx;
   qmi_ctx->int_txn_buf = int_buf;
 
   // create port to watch for interrupts and channel messages
@@ -768,8 +766,6 @@
     // the total transmission size
     tx_buf->header.send_zlp = true;
 
-    tx_buf->complete_cb = usb_write_complete;
-    tx_buf->cookie = qmi_ctx;
     zx_status_t status = usb_req_list_add_head(&qmi_ctx->tx_txn_bufs, tx_buf,
                                                qmi_ctx->parent_req_size);
     ZX_DEBUG_ASSERT(status == ZX_OK);
@@ -789,8 +785,6 @@
       goto fail;
     }
 
-    rx_buf->complete_cb = usb_read_complete;
-    rx_buf->cookie = qmi_ctx;
     usb_request_queue(&qmi_ctx->usb, rx_buf, usb_read_complete, qmi_ctx);
     rx_buf_remain -= rx_buf_sz;
   }
diff --git a/drivers/usb_video/usb-video-stream.cpp b/drivers/usb_video/usb-video-stream.cpp
index 9231e11..7ba7ecb 100644
--- a/drivers/usb_video/usb-video-stream.cpp
+++ b/drivers/usb_video/usb-video-stream.cpp
@@ -172,11 +172,6 @@
       return status;
     }
 
-    req->cookie = this;
-    req->complete_cb = [](usb_request_t* req, void* cookie) -> void {
-      ZX_DEBUG_ASSERT(cookie != nullptr);
-      reinterpret_cast<UsbVideoStream*>(cookie)->RequestComplete(req);
-    };
     status = usb_req_list_add_head(&free_reqs_, req, parent_req_size_);
     ZX_DEBUG_ASSERT(status == ZX_OK);
     num_free_reqs_++;
diff --git a/drivers/wlan/mediatek/ralink/device.cpp b/drivers/wlan/mediatek/ralink/device.cpp
index 11e9f75..cc62ca0 100644
--- a/drivers/wlan/mediatek/ralink/device.cpp
+++ b/drivers/wlan/mediatek/ralink/device.cpp
@@ -3652,8 +3652,6 @@
             errorf("failed to allocate rx usb request\n");
             return status;
         }
-        req->complete_cb = &Device::ReadRequestComplete;
-        req->cookie = this;
         usb_request_queue(&usb_, req, &Device::ReadRequestComplete, this);
     }
     // Only one TX queue for now
@@ -3666,8 +3664,6 @@
             errorf("failed to allocate tx usb request\n");
             return status;
         }
-        req->complete_cb = &Device::WriteRequestComplete;
-        req->cookie = this;
         free_write_reqs_.push_back(req);
     }
 
diff --git a/drivers/wlan/third_party/broadcom/brcmfmac/usb.c b/drivers/wlan/third_party/broadcom/brcmfmac/usb.c
index bb24131..2b4a4c5 100644
--- a/drivers/wlan/third_party/broadcom/brcmfmac/usb.c
+++ b/drivers/wlan/third_party/broadcom/brcmfmac/usb.c
@@ -230,8 +230,6 @@
     }
     urb->context = context;
     urb->devinfo = devinfo;
-    zxurb->cookie = urb;
-    zxurb->complete_cb = complete;
     zxurb->header.length = size;
     zxurb->header.ep_address = ep_address;
     zxurb->header.send_zlp = zero_packet;