rtc: rtc-sh: Zero out tm value for invalid rtc states.

Follows the changes of some of the other RTC drivers. If the tm
value is bogus, just zero it out. Adds some sanity for RTC_RD_TIME.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

drivers/rtc/rtc-sh.c

@@ -351,8 +351,10 @@ static int sh_rtc_read_time(struct device *dev, struct rtc_time *tm)
 		tm->tm_sec, tm->tm_min, tm->tm_hour,
 		tm->tm_mday, tm->tm_mon + 1, tm->tm_year, tm->tm_wday);
 
-	if (rtc_valid_tm(tm) < 0)
+	if (rtc_valid_tm(tm) < 0) {
 		dev_err(dev, "invalid date\n");
+		rtc_time_to_tm(0, tm);
+	}
 
 	return 0;
 }