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/ds1302.c b/drivers/rtc/ds1302.c
index 55af130..3a856c8 100644
--- a/drivers/rtc/ds1302.c
+++ b/drivers/rtc/ds1302.c
@@ -253,9 +253,10 @@
 	/* TODO */
 }
 
-void
+int
 rtc_get(struct rtc_time *tmp)
 {
+	int rel = 0;
 	struct ds1302_st bbclk;
 
 	if(!ds1302_initted) rtc_init();
@@ -265,6 +266,7 @@
 	if (bbclk.CH) {
 		printf("ds1302: rtc_get: Clock was halted, clock probably "
 			"corrupt\n");
+		rel = -1;
 	}
 
 	tmp->tm_sec=10*bbclk.sec10+bbclk.sec;
@@ -281,6 +283,8 @@
 	DPRINTF("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;
 }
 
 void