drm/etnaviv: fix missing unlock on error in etnaviv_gpu_submit()

Add the missing unlock before return from function etnaviv_gpu_submit()
in the error handling case.

lst: fixed label name.

Fixes: f3cd1b064f11 ("drm/etnaviv: (re-)protect fence allocation with
GPU mutex")
CC: stable@vger.kernel.org #4.9+
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>

drivers/gpu/drm/etnaviv/etnaviv_gpu.c

@@ -1317,7 +1317,7 @@ int etnaviv_gpu_submit(struct etnaviv_gpu *gpu,
 	if (!fence) {
 		event_free(gpu, event);
 		ret = -ENOMEM;
-		goto out_pm_put;
+		goto out_unlock;
 	}
 
 	gpu->event[event].fence = fence;
@@ -1357,6 +1357,7 @@ int etnaviv_gpu_submit(struct etnaviv_gpu *gpu,
 	hangcheck_timer_reset(gpu);
 	ret = 0;
 
+out_unlock:
 	mutex_unlock(&gpu->lock);
 
 out_pm_put: