rtc: mc13xxx: fix a double-unlock issue

In function mc13xxx_rtc_probe, the mc13xxx_unlock() is called
before rtc_register_device(). But in the error path of
rtc_register_device(), the mc13xxx_unlock() is called again,
which causes a double-unlock problem. Thus add a call of the
function “mc13xxx_lock” in an if branch for the completion
of the exception handling.

Fixes: e4ae7023 ("rtc: mc13xxx: set range")
Signed-off-by: Qiushi Wu <wu000273@umn.edu>
Link: https://lore.kernel.org/r/20200503182235.1652-1-wu000273@umn.eduSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-mc13xxx.c

@@ -308,8 +308,10 @@ static int __init mc13xxx_rtc_probe(struct platform_device *pdev)
 	mc13xxx_unlock(mc13xxx);
 
 	ret = rtc_register_device(priv->rtc);
-	if (ret)
+	if (ret) {
+		mc13xxx_lock(mc13xxx);
 		goto err_irq_request;
+	}
 
 	return 0;