rtc: allow rtc_set to return an error and use it in cmd_date

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/board/etin/debris/phantom.c b/board/etin/debris/phantom.c
index 263da6b..48b81f7 100644
--- a/board/etin/debris/phantom.c
+++ b/board/etin/debris/phantom.c
@@ -254,7 +254,7 @@
 	return 0;
 }
 
-void rtc_set( struct rtc_time *tmp )
+int rtc_set( struct rtc_time *tmp )
 {
 	if (phantom_flag < 0)
 		phantom_flag = get_phantom_flag();
@@ -307,6 +307,8 @@
 		/* unlock clock registers after read */
 		rtc_write( RTC_CONTROLA, ( reg_a  & ~RTC_CA_WRITE ));
 	}
+
+	return 0;
 }
 
 #endif