rtc: allow rtc_set to return an error and use it in cmd_date

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/drivers/rtc/s3c24x0_rtc.c b/drivers/rtc/s3c24x0_rtc.c
index 13d077b..0d3372f 100644
--- a/drivers/rtc/s3c24x0_rtc.c
+++ b/drivers/rtc/s3c24x0_rtc.c
@@ -135,7 +135,7 @@
 	return 0;
 }
 
-void rtc_set (struct rtc_time *tmp)
+int rtc_set (struct rtc_time *tmp)
 {
 	S3C24X0_RTC * const rtc = S3C24X0_GetBase_RTC();
 	uchar sec, min, hour, mday, wday, mon, year;
@@ -167,6 +167,8 @@
 
 	/* disable access to RTC registers */
 	SetRTC_Access(RTC_DISABLE);
+
+	return 0;
 }
 
 void rtc_reset (void)