sony-laptop - remove private workqueue, use keventd instead

If we reschedule work instead of having work function sleep for 10 msecs
between reads from kfifo we can safely use the main workqueue (keventd)
and not bother with creating driver-private one.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Len Brown <len.brown@intel.com>