drm/amdgpu: fix ocl test performance drop

partial revert commit <6971d3d> - drm/amdgpu: cleanup logic in
amdgpu_vm_flush

Signed-off-by: Flora Cui <Flora.Cui@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <David1.Zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -743,8 +743,7 @@ int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job)
 		id->gws_size != job->gws_size ||
 		id->oa_base != job->oa_base ||
 		id->oa_size != job->oa_size);
-	bool vm_flush_needed = job->vm_needs_flush ||
-		amdgpu_vm_ring_has_compute_vm_bug(ring);
+	bool vm_flush_needed = job->vm_needs_flush;
 	unsigned patch_offset = 0;
 	int r;