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/pl031.c b/drivers/rtc/pl031.c
index e6c1a6c..fc83049 100644
--- a/drivers/rtc/pl031.c
+++ b/drivers/rtc/pl031.c
@@ -72,8 +72,7 @@
 	}
 
 	/* Calculate number of seconds this incoming time represents */
-	tim = mktime(tmp->tm_year, tmp->tm_mon, tmp->tm_mday,
-			tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
+	tim = rtc_mktime(tmp);
 
 	RTC_WRITE_REG(RTC_LR, tim);