iwlagn: fix PAN queues

Currently, when a PAN queue needs to be
stopped, we erroneously stop queue number 5
(for example) with mac80211 -- which doesn't
even exist!

To avoid that problem, recalculate the swq_id
for all queues when setting up the queues,
and don't use the default identity mapping
that is acceptable for devices which don't
support PAN.

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