platform/x86: intel-hid: Missing power button release on some Dell models

Power button suspend for some Dell models was added in:

commit 821b8536 ("platform/x86: intel-hid: Power button suspend on Dell Latitude 7275")

by checking against the power button press notification (0xCE) to report
the power button press event. The corresponding power button release
notification (0xCF) was caught and ignored to stop it from being reported
as an "unknown event" in the logs.

The missing button release event is creating issues on Android-x86, as
reported on the project mailing list for a Dell Latitude 5175 model, since
the events are expected in down/up pairs.

Report the power button release event to fix this issue.

Link: https://groups.google.com/forum/#!topic/android-x86/aSwZK9Nf9Ro


Tested-by: Tristian Celestin <tristian.celestin@outlook.com>
Tested-by: Jérôme de Bretagne <jerome.debretagne@gmail.com>
Signed-off-by: Jérôme de Bretagne <jerome.debretagne@gmail.com>
Reviewed-by: Mario Limonciello <mario.limonciello@dell.com>
[dvhart: corrected commit reference format per checkpatch]
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>