drm/amdgpu: add function parameter description in 'amdgpu_gart_bind'

Fixes gcc warning:

drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c:313: warning: Function
parameter or member 'flags' not described in 'amdgpu_gart_bind'

Fixes: d38ceaf99e ("drm/amdgpu: add core driver (v4)")
Signed-off-by: yu kuai <yukuai3@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c

@@ -302,6 +302,7 @@ int amdgpu_gart_map(struct amdgpu_device *adev, uint64_t offset,
  * @pages: number of pages to bind
  * @pagelist: pages to bind
  * @dma_addr: DMA addresses of pages
+ * @flags: page table entry flags
  *
  * Binds the requested pages to the gart page table
  * (all asics).