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/ds1306.c b/drivers/rtc/ds1306.c
index 3fe6721..7dd3e19 100644
--- a/drivers/rtc/ds1306.c
+++ b/drivers/rtc/ds1306.c
@@ -180,8 +180,7 @@
 	{
 		ulong tim;
 
-		tim = mktime (tmp->tm_year, tmp->tm_mon, tmp->tm_mday,
-			      tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
+		tim = rtc_mktime(tmp);
 
 		immap->im_sitk.sitk_rtck = KAPWR_KEY;
 		immap->im_sit.sit_rtc = tim;