This little patch changes the way button release events are reported
by the sonypi driver to the application: previously, separate
release events were detected for each button. However, many buttons
(example: the jogdial, the capture button, the back button etc) share
the same release event.

The attached patch propagates a single 'ANYBUTTON_RELEASED' event
to the userspace, leaving all state machine intelligence to the
application.

Kunihiko IMAI should be credited for his ideas and tests.