hp-wmi: fix rfkill memory leak on unload

rfkill_unregister() should always be followed by rfkill_destroy()
In this case, rfkill_destroy was called two times on wifi_rfkill and
never on bluetooth_rfkill.

Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Acked-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Len Brown <len.brown@intel.com>