rfkill: add the GPS radio type

Althoug GPS is a technology w/o transmitting radio
and thus not a primary candidate for rfkill switch,
rfkill gives unified interface point for devices with
wireless technology.

The input key is not supplied as it is too be deprecated.

Cc: johannes@sipsolutions.net
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>