of: unittest: Unlock on error in unittest_data_add()

The of_overlay_mutex_unlock() was accidentally deleted if "of_root" is
NULL. Change this to a goto unlock.

Fixes: d1eabd218ede ("of: unittest: treat missing of_root as error instead of fixing up")
Signed-off-by: Dan Carpenter <[e-mail]>
Reviewed-by: Stephen Boyd <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring (Arm) <[e-mail]>

drivers/of/unittest.c

···
 	rc = of_resolve_phandles(unittest_data_node);
 	if (rc) {
 		pr_err("%s: Failed to resolve phandles (rc=%i)\n", __func__, rc);
-		of_overlay_mutex_unlock();
-		return -EINVAL;
+		rc = -EINVAL;
+		goto unlock;
 	}
 
 	/* attach the sub-tree to live tree */
 	if (!of_root) {
 		pr_warn("%s: no live tree to attach sub-tree\n", __func__);
 		kfree(unittest_data);
-		return -ENODEV;
+		rc = -ENODEV;
+		goto unlock;
 	}
 
 	EXPECT_BEGIN(KERN_INFO,
···
 	EXPECT_END(KERN_INFO,
 		   "Duplicate name in testcase-data, renamed to \"duplicate-name#1\"");
 
+unlock:
 	of_overlay_mutex_unlock();
 
-	return 0;
+	return rc;
 }
 
 #ifdef CONFIG_OF_OVERLAY