drm/amdgpu: add nbio callbacks for vcn doorbell support

For Navi10 VCN2.0, the engine supports Doorbell
Signed-off-by: NLeo Liu <leo.liu@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

@@ -659,6 +659,8 @@ struct amdgpu_nbio_funcs {
 	u32 (*get_memsize)(struct amdgpu_device *adev);
 	void (*sdma_doorbell_range)(struct amdgpu_device *adev, int instance,
 			bool use_doorbell, int doorbell_index, int doorbell_size);
+	void (*vcn_doorbell_range)(struct amdgpu_device *adev, bool use_doorbell,
+			int doorbell_index);
 	void (*enable_doorbell_aperture)(struct amdgpu_device *adev,
 					 bool enable);
 	void (*enable_doorbell_selfring_aperture)(struct amdgpu_device *adev,