x86/olpc/xo1/sci: Report RTC wakeup events

When the system is woken due to a RTC event, report the wakeup
event on the relevant rtc device (if it can be found).

Signed-off-by: Daniel Drake <dsd@laptop.org>
Cc: dilinger@queued.net
Cc: pgf@laptop.org
Link: http://lkml.kernel.org/r/20120418223402.D73249D401E@zog.reactivated.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>