LWMON5: POST RTC fix

Modify the RTC API to provide one a status for the time reported by
the rtc_get() function:
  0 - a reliable time is guaranteed,
< 0 - a reliable time isn't guaranteed (power fault, clock issues,
      and so on).

The RTC chip drivers are responsible for providing this info if the
corresponding chip supports such functionality. If not - always
report that the time is reliable.

The POST RTC test was modified to detect the RTC faults utilizing
this new rtc_get() feature.

Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
diff --git a/drivers/rtc/s3c24x0_rtc.c b/drivers/rtc/s3c24x0_rtc.c
index 7f8b4fa..358aef7 100644
--- a/drivers/rtc/s3c24x0_rtc.c
+++ b/drivers/rtc/s3c24x0_rtc.c
@@ -70,7 +70,7 @@
 
 /* ------------------------------------------------------------------------- */
 
-void rtc_get (struct rtc_time *tmp)
+int rtc_get (struct rtc_time *tmp)
 {
 	S3C24X0_RTC * const rtc = S3C24X0_GetBase_RTC();
 	uchar sec, min, hour, mday, wday, mon, year;
@@ -131,6 +131,8 @@
 		tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
 		tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
 #endif
+
+	return 0;
 }
 
 void rtc_set (struct rtc_time *tmp)