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/board/mousse/m48t59y.c b/board/mousse/m48t59y.c
index 37a6244..2c1e6cf 100644
--- a/board/mousse/m48t59y.c
+++ b/board/mousse/m48t59y.c
@@ -278,7 +278,7 @@
 /*
  * U-Boot RTC support.
  */
-void
+int
 rtc_get( struct rtc_time *tmp )
 {
 	m48_tod_get(&tmp->tm_year,
@@ -295,6 +295,8 @@
 		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