sparc64: Check for RTC class device in update_persistent_clock().

As we convert the various by-hand sparc64 RTC drivers to use the
generic RTC framework and drivers, we need to keep the NTP
set_rtc_mmss() support via update_persistent_clock() working.

In the end, after all the RTC device cases are converted, this
local set_rtc_mmss() function will be deleted.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

arch/sparc64/kernel/time.c

@@ -405,6 +405,11 @@ static unsigned long timer_ticks_per_nsec_quotient __read_mostly;
 
 int update_persistent_clock(struct timespec now)
 {
+	struct rtc_device *rtc = rtc_class_open("rtc0");
+
+	if (rtc)
+		return rtc_set_mmss(rtc, now.tv_sec);
+
 	return set_rtc_mmss(now.tv_sec);
 }