Platform: hp-wmi: add rfkill support for integrated GPS

Add rfkill support for the GPS radio found in HP laptops (HP Elitebook 2170p and the like)
using the Ericsson F5321/H5321 Mobile Broadband Module.

Signed-off-by: Viliam Trepák <trepo@netcomga.sk>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>