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/isl1208.c b/drivers/rtc/isl1208.c
index d872802..3d46fd0 100644
--- a/drivers/rtc/isl1208.c
+++ b/drivers/rtc/isl1208.c
@@ -73,8 +73,9 @@
  * Get the current time from the RTC
  */
 
-void rtc_get (struct rtc_time *tmp)
+int rtc_get (struct rtc_time *tmp)
 {
+	int rel = 0;
 	uchar sec, min, hour, mday, wday, mon, year, status;
 
 	status = rtc_read (RTC_STAT_REG_ADDR);
@@ -94,6 +95,7 @@
 		printf ("### Warning: RTC oscillator has stopped\n");
 		rtc_write(RTC_STAT_REG_ADDR,
 			rtc_read(RTC_STAT_REG_ADDR) &~ (RTC_STAT_BIT_BAT|RTC_STAT_BIT_RTCF));
+		rel = -1;
 	}
 
 	tmp->tm_sec  = bcd2bin (sec & 0x7F);
@@ -109,6 +111,8 @@
 	DEBUGR ("Get DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
 		tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
 		tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
+
+	return rel;
 }
 
 /*