[ddk][io-buffer] Tag old init functions as __DDK_DEPRECATE

This will make things less noisy for most people than __DEPRECATE.

ZX-1838 #done

Change-Id: If22ecaf81de636b54dab390d94dd45254d55f8f4
diff --git a/system/ulib/ddk/include/ddk/io-buffer.h b/system/ulib/ddk/include/ddk/io-buffer.h
index 720287d..fff3647 100644
--- a/system/ulib/ddk/include/ddk/io-buffer.h
+++ b/system/ulib/ddk/include/ddk/io-buffer.h
@@ -71,13 +71,13 @@
                                              zx_handle_t resource, uint32_t cache_policy);
 
 // Legacy variants of the above
-zx_status_t io_buffer_init(io_buffer_t* buffer, size_t size, uint32_t flags) __DEPRECATE;
+zx_status_t io_buffer_init(io_buffer_t* buffer, size_t size, uint32_t flags) __DDK_DEPRECATE;
 zx_status_t io_buffer_init_aligned(io_buffer_t* buffer, size_t size, uint32_t alignment_log2,
-                                   uint32_t flags) __DEPRECATE;
+                                   uint32_t flags) __DDK_DEPRECATE;
 zx_status_t io_buffer_init_vmo(io_buffer_t* buffer, zx_handle_t vmo_handle,
-                               zx_off_t offset, uint32_t flags) __DEPRECATE;
+                               zx_off_t offset, uint32_t flags) __DDK_DEPRECATE;
 zx_status_t io_buffer_init_physical(io_buffer_t* buffer, zx_paddr_t addr, size_t size,
-                                    zx_handle_t resource, uint32_t cache_policy) __DEPRECATE;
+                                    zx_handle_t resource, uint32_t cache_policy) __DDK_DEPRECATE;
 
 zx_status_t io_buffer_cache_op(io_buffer_t* buffer, const uint32_t op,
                                const zx_off_t offset, const size_t size);