tcmu: Add a missing unlock on an error path

We added a new error path here but we forgot to drop the lock first
before returning.

Fixes: 0d44374c1aae ("tcmu: fix double se_cmd completion")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_user.c

@@ -888,6 +888,7 @@ tcmu_queue_cmd_ring(struct tcmu_cmd *tcmu_cmd)
 	ret = tcmu_setup_cmd_timer(tcmu_cmd);
 	if (ret) {
 		tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cnt);
+		mutex_unlock(&udev->cmdr_lock);
 		return TCM_OUT_OF_RESOURCES;
 	}
 	entry->hdr.cmd_id = tcmu_cmd->cmd_id;