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/mx27rtc.c b/drivers/rtc/mx27rtc.c
index 7ba74d3..29ccdf1 100644
--- a/drivers/rtc/mx27rtc.c
+++ b/drivers/rtc/mx27rtc.c
@@ -40,8 +40,7 @@
 	struct rtc_regs *rtc_regs = (struct rtc_regs *)IMX_RTC_BASE;
 	uint32_t day, hour, min, sec;
 
-	sec = mktime(time->tm_year, time->tm_mon, time->tm_mday,
-		time->tm_hour, time->tm_min, time->tm_sec);
+	sec = rtc_mktime(time);
 
 	day  = sec / (24 * 3600);
 	sec  = sec % (24 * 3600);