test_firmware: fix missing unlock on error in config_num_requests_store()

commit a5e1923356505e46476c2fb518559b7a4d9d25b1 upstream.

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

Fixes: c92316bf8e94 ("test_firmware: add batched firmware tests")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/lib/test_firmware.c b/lib/test_firmware.c
index 64a4c76..e700868 100644
--- a/lib/test_firmware.c
+++ b/lib/test_firmware.c
@@ -371,6 +371,7 @@
 	if (test_fw_config->reqs) {
 		pr_err("Must call release_all_firmware prior to changing config\n");
 		rc = -EINVAL;
+		mutex_unlock(&test_fw_mutex);
 		goto out;
 	}
 	mutex_unlock(&test_fw_mutex);