drm/amdgpu: Add new ring callback to insert memory sync

Used to flush and invalidate various caches.

v2: Rename function hook
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h

@@ -195,6 +195,7 @@ struct amdgpu_ring_funcs {
 	/* Try to soft recover the ring to make the fence signal */
 	void (*soft_recovery)(struct amdgpu_ring *ring, unsigned vmid);
 	int (*preempt_ib)(struct amdgpu_ring *ring);
+	void (*emit_mem_sync)(struct amdgpu_ring *ring);
 };
 
 struct amdgpu_ring {