drm/nouveau: no need to update bo.offset from vma after validate

On chipsets using nouveau_vm, the virtual address stays constant, so
the value set at bo creation time is fine.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -312,8 +312,6 @@ nouveau_bo_validate(struct nouveau_bo *nvbo, bool interruptible,
 	if (ret)
 		return ret;
 
-	if (nvbo->vma.node)
-		nvbo->bo.offset = nvbo->vma.offset;
 	return 0;
 }