drm/amdgpu: stop waiting in amdgpu_uvd_send_msg

We have a wait in the amdgpu_bo_kmap() code for quite a while now, so
waiting here isn't needed any more.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>