drm/amdgpu/sdma4: add emit_reg_write_reg_wait ring callback (v2)

This adds support for writing and reading back in a single
oneshot packet.  This is needed to send a tlb invalidation
and wait for ack in a single operation.

v2: squash sdma hang fix into this patch
Reviewed-by: NHuang Rui <ray.huang@amd.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NEmily Deng <Emily.Deng@amd.com>

drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c

@@ -1611,6 +1611,7 @@ static const struct amdgpu_ring_funcs sdma_v4_0_ring_funcs = {
 	.pad_ib = sdma_v4_0_ring_pad_ib,
 	.emit_wreg = sdma_v4_0_ring_emit_wreg,
 	.emit_reg_wait = sdma_v4_0_ring_emit_reg_wait,
+	.emit_reg_write_reg_wait = amdgpu_ring_emit_reg_write_reg_wait_helper,
 };
 
 static void sdma_v4_0_set_ring_funcs(struct amdgpu_device *adev)