drm/amdgpu: stop syncing PRT map operations

Requested by both Bas and Friedrich. Mapping PTEs as PRT doesn't need to
sync for anything.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Friedrich Vock <friedrich.vock@gmx.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1161,7 +1161,7 @@ int amdgpu_vm_bo_update(struct amdgpu_device *adev, struct amdgpu_bo_va *bo_va,
 	int r;
 
 	amdgpu_sync_create(&sync);
-	if (clear || !bo) {
+	if (clear) {
 		mem = NULL;
 
 		/* Implicitly sync to command submissions in the same VM before
@@ -1176,6 +1176,10 @@ int amdgpu_vm_bo_update(struct amdgpu_device *adev, struct amdgpu_bo_va *bo_va,
 			if (r)
 				goto error_free;
 		}
+	} else if (!bo) {
+		mem = NULL;
+
+		/* PRT map operations don't need to sync to anything. */
 
 	} else {
 		struct drm_gem_object *obj = &bo->tbo.base;