amdgpu: add padding to the fence to handle ioctl.

I don't think this ioctl is in a Linus release yet.
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

include/uapi/drm/amdgpu_drm.h

@@ -553,6 +553,7 @@ union drm_amdgpu_fence_to_handle {
 	struct {
 		struct drm_amdgpu_fence fence;
 		__u32 what;
+		__u32 pad;
 	} in;
 	struct {
 		__u32 handle;