drm/amdgpu: add missing error handling in function amdgpu_gmc_flush_gpu_tlb_pasid

Fix the unchecked return value warning reported by Coverity,
so add error handling.
Signed-off-by: Bob Zhou <bob.zhou@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -718,7 +718,11 @@ int amdgpu_gmc_flush_gpu_tlb_pasid(struct amdgpu_device *adev, uint16_t pasid,
 			ndw += kiq->pmf->invalidate_tlbs_size;
 
 		spin_lock(&adev->gfx.kiq[inst].ring_lock);
-		amdgpu_ring_alloc(ring, ndw);
+		r = amdgpu_ring_alloc(ring, ndw);
+		if (r) {
+			spin_unlock(&adev->gfx.kiq[inst].ring_lock);
+			goto error_unlock_reset;
+		}
 		if (adev->gmc.flush_tlb_needs_extra_type_2)
 			kiq->pmf->kiq_invalidate_tlbs(ring, pasid, 2, all_hub);