drm/nouveau: fix runtime pm imbalance on error

pm_runtime_get_sync() increments the runtime PM usage counter even
the call returns an error code. Thus a pairing decrement is needed
on the error handling path to keep the counter balanced.

Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_gem.c

@@ -159,8 +159,8 @@ nouveau_gem_object_close(struct drm_gem_object *gem, struct drm_file *file_priv)
 			if (!WARN_ON(ret < 0 && ret != -EACCES)) {
 				nouveau_gem_object_unmap(nvbo, vma);
 				pm_runtime_mark_last_busy(dev);
-				pm_runtime_put_autosuspend(dev);
 			}
+			pm_runtime_put_autosuspend(dev);
 		}
 	}
 	ttm_bo_unreserve(&nvbo->bo);