x86/olpc/xo1/sci: Produce wakeup events for buttons and switches

Produce wakeup events for the XO-1's power button, lid switch
and ebook switch, taking care to only produce events when the
states have changed.

Signed-off-by: Daniel Drake <dsd@laptop.org>
Cc: dilinger@queued.net
Cc: pgf@laptop.org
Link: http://lkml.kernel.org/r/20120412171824.D14C49D401E@zog.reactivated.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>