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/ds1306.c b/drivers/rtc/ds1306.c
index 89e433d..1c8ac7f 100644
--- a/drivers/rtc/ds1306.c
+++ b/drivers/rtc/ds1306.c
@@ -91,7 +91,7 @@
 /* ------------------------------------------------------------------------- */
 
 /* read clock time from DS1306 and return it in *tmp */
-void rtc_get (struct rtc_time *tmp)
+int rtc_get (struct rtc_time *tmp)
 {
 	volatile immap_t *immap = (immap_t *) CFG_IMMR;
 	unsigned char spi_byte;	/* Data Byte */
@@ -141,6 +141,8 @@
 	debug ("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 0;
 }
 
 /* ------------------------------------------------------------------------- */
@@ -304,7 +306,7 @@
 static void rtc_write (unsigned char reg, unsigned char val);
 
 /* read clock time from DS1306 and return it in *tmp */
-void rtc_get (struct rtc_time *tmp)
+int rtc_get (struct rtc_time *tmp)
 {
 	unsigned char sec, min, hour, mday, wday, mon, year;
 
@@ -349,6 +351,8 @@
 	debug ("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 0;
 }
 
 /* ------------------------------------------------------------------------- */