[Saucy][Trusty SRU] hp-wireless: handle new wireless hotkey button

[Alex Hung]

SRU Justification:

Impact:
  With the introduction of _OSI("Windows 2012") = true in Linux kernel, BIOS
  changes its behaviours for wireless hotkey. As a result, the original
  implementation in hp-wmi no longer works.

Fix:
  BIOS declares a new ACPI device for the wireless hotkey and a new kernel
  module is created to handle its event generated by pressing the hotkey.

  The patches are included in upstream and are cherry-picked from Linus's repo.

BugLink: http://bugs.launchpad.net/bugs/1303737