dm: rtc: Rename mktime() and reduce the number of parameters

Most callers unpack the structure and pass each member. It seems better to
pass the whole structure instead, as with the C library. Also add an rtc_
prefix.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Heiko Schocher <hs@denx.de>
diff --git a/drivers/rtc/mpc8xx.c b/drivers/rtc/mpc8xx.c
index 796295d..147a225 100644
--- a/drivers/rtc/mpc8xx.c
+++ b/drivers/rtc/mpc8xx.c
@@ -44,8 +44,7 @@
 		tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
 		tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
 
-	tim = mktime (tmp->tm_year, tmp->tm_mon, tmp->tm_mday,
-		      tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
+	tim = rtc_mktime(tmp);
 
 	immr->im_sitk.sitk_rtck = KAPWR_KEY;
 	immr->im_sit.sit_rtc = tim;