iwlagn: use IWL_MAX_TID_COUNT for WoWLAN

Now that I corrected IWL_MAX_TID_COUNT to be 8
instead of 9, we can use it in WoWLAN suspend.

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