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/ds1374.c b/drivers/rtc/ds1374.c
index 04793b5..7847357 100644
--- a/drivers/rtc/ds1374.c
+++ b/drivers/rtc/ds1374.c
@@ -147,9 +147,7 @@
 	if (tmp->tm_year < 1970 || tmp->tm_year > 2069)
 		printf("WARNING: year should be between 1970 and 2069!\n");
 
-	time = mktime(tmp->tm_year, tmp->tm_mon,
-			tmp->tm_mday, tmp->tm_hour,
-			tmp->tm_min, tmp->tm_sec);
+	time = rtc_mktime(tmp);
 
 	DEBUGR ("Set RTC s since 1.1.1970: %ld (0x%02lx)\n", time, time);