mc146818rtc: register the clock reset notifier on the right clock

Commit 884f17c2 (aio / timers: Convert rtc_clock to be a QEMUClockType,
2013-08-21) erroneously changed an occurrence of rtc_clock to
QEMU_CLOCK_REALTIME, which broke the RTC reset notifier in
mc146818rtc.  Fix this.

I redid the patch myself since the original reporter did not sign
off on his.

Cc: qemu-stable@nongnu.org
Reported-by: NLb peace <peaceustc@gmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 13c0cbae)
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>

hw/timer/mc146818rtc.c

@@ -852,7 +852,7 @@ static void rtc_realizefn(DeviceState *dev, Error **errp)
     check_update_timer(s);
 
     s->clock_reset_notifier.notify = rtc_notify_clock_reset;
-    qemu_clock_register_reset_notifier(QEMU_CLOCK_REALTIME,
+    qemu_clock_register_reset_notifier(rtc_clock,
                                        &s->clock_reset_notifier);
 
     s->suspend_notifier.notify = rtc_notify_suspend;