drm/amd/amdgpu/amdgpu_device: Provide suitable description for param 'xcc_id'

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c:516: warning: Function parameter or member 'xcc_id' not described in 'amdgpu_mm_wreg_mmio_rlc'
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -507,6 +507,7 @@ void amdgpu_device_wreg(struct amdgpu_device *adev,
  * @adev: amdgpu_device pointer
  * @reg: mmio/rlc register
  * @v: value to write
+ * @xcc_id: xcc accelerated compute core id
  *
  * this function is invoked only for the debugfs register access
  */