drm/amd/amdgpu/gmc_v9_0: Suppy some missing function doc descriptions

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

 drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c:382:23: warning: ‘ecc_umc_mcumc_status_addrs’ defined but not used [-Wunused-const-variable=]
 drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c:720: warning: Function parameter or member 'vmhub' not described in 'gmc_v9_0_flush_gpu_tlb'
 drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c:836: warning: Function parameter or member 'flush_type' not described in 'gmc_v9_0_flush_gpu_tlb_pasid'
 drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c:836: warning: Function parameter or member 'all_hub' not described in 'gmc_v9_0_flush_gpu_tlb_pasid'

Acked-by: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c

@@ -691,6 +691,7 @@ static bool gmc_v9_0_get_atc_vmid_pasid_mapping_info(struct amdgpu_device *adev,
  *
  * @adev: amdgpu_device pointer
  * @vmid: vm instance to flush
+ * @vmhub: which hub to flush
  * @flush_type: the flush type
  *
  * Flush the TLB for the requested page table using certain type.
@@ -807,6 +808,8 @@ static void gmc_v9_0_flush_gpu_tlb(struct amdgpu_device *adev, uint32_t vmid,
  *
  * @adev: amdgpu_device pointer
  * @pasid: pasid to be flush
+ * @flush_type: the flush type
+ * @all_hub: flush all hubs
  *
  * Flush the TLB for the requested pasid.
  */