iwlagn: init cmd_queue earlier

We know after loading the ucode whether it will
support PAN or not, so we can also initialise
the cmd_queue variable much earlier.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>