[usb-request] Move some definitions to the correct header file

TEST: builds
Change-Id: I01ac93c34659064aaa9898834a8dc2a9bc927440
diff --git a/system/dev/lib/usb/include/usb/usb-request.h b/system/dev/lib/usb/include/usb/usb-request.h
index cdd88e0..895a0f1 100644
--- a/system/dev/lib/usb/include/usb/usb-request.h
+++ b/system/dev/lib/usb/include/usb/usb-request.h
@@ -16,6 +16,12 @@
 
 __BEGIN_CDECLS;
 
+// cache maintenance ops
+#define USB_REQUEST_CACHE_INVALIDATE        ZX_VMO_OP_CACHE_INVALIDATE
+#define USB_REQUEST_CACHE_CLEAN             ZX_VMO_OP_CACHE_CLEAN
+#define USB_REQUEST_CACHE_CLEAN_INVALIDATE  ZX_VMO_OP_CACHE_CLEAN_INVALIDATE
+#define USB_REQUEST_CACHE_SYNC              ZX_VMO_OP_CACHE_SYNC
+
 typedef struct {
     list_node_t free_reqs;
     mtx_t lock;
diff --git a/system/ulib/ddk/include/ddk/protocol/usb-old.h b/system/ulib/ddk/include/ddk/protocol/usb-old.h
index 54d2491..c971973 100644
--- a/system/ulib/ddk/include/ddk/protocol/usb-old.h
+++ b/system/ulib/ddk/include/ddk/protocol/usb-old.h
@@ -15,14 +15,6 @@
 
 __BEGIN_CDECLS;
 
-typedef struct usb_request usb_request_t;
-
-// cache maintenance ops
-#define USB_REQUEST_CACHE_INVALIDATE        ZX_VMO_OP_CACHE_INVALIDATE
-#define USB_REQUEST_CACHE_CLEAN             ZX_VMO_OP_CACHE_CLEAN
-#define USB_REQUEST_CACHE_CLEAN_INVALIDATE  ZX_VMO_OP_CACHE_CLEAN_INVALIDATE
-#define USB_REQUEST_CACHE_SYNC              ZX_VMO_OP_CACHE_SYNC
-
 typedef void (*usb_request_complete_cb)(usb_request_t* req, void* cookie);
 
 // Returns a batch of completed requests for an endpoint.