asus-laptop: Add rfkill support for Pegatron Lucid tablet

Add three new rfkill switches in this driver that are specific to
Pegatron Lucid tablet.
Please note that you might not need all three switches. For example if
you don't have a 3G module inside your tablet.

Also, on my device, the gpio for the wifi/bt module is connected to the
bluetooth line. Therefore to activate your wireless lan interface, you
need to use the "pega-bt" rfkill switch.

Finally, the rfkill switch only works before the wireless module is
loaded the first time. Unloading ath9k doesn't help, a reboot is
necessary.

Signed-off-by: Anisse Astier <anisse@astier.eu>
Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Matthew Garrett <mjg@redhat.com>