drivers/rtc/interface.c: check the error after __rtc_read_time()

In __rtc_set_alarm(), the error after __rtc_read_time() is not checked.
If rtc device fail to read time, we cannot guarantee the following
process.

Add the verification code for returned __rtc_read_time() error.
Signed-off-by: NHyogi Gim <hyogi.gim@lge.com>
Acked-by: NAlessandro Zummo <a.zummo@towertech.it>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/interface.c

@@ -348,6 +348,8 @@ static int __rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 
 	/* Make sure we're not setting alarms in the past */
 	err = __rtc_read_time(rtc, &tm);
+	if (err)
+		return err;
 	rtc_tm_to_time(&tm, &now);
 	if (scheduled <= now)
 		return -ETIME;