iwlwifi: prepare for PAN queue/fifo assignment

PAN ucode will require a different queue assignment,
in particular queue 9 instead of 4 should be used for
commands.

This is required because the ucode will stop/start
queues 4 and 8 depending on the PAN state, since
queue 8 will be used for PAN multicast (after DTIM).

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