wifi: iwlwifi: mvm: fix the TXF mapping for BZ devices

wifi: iwlwifi: mvm: fix the TXF mapping for BZ devices

Those devices' fifos are numbered differently.
Because of that, we were looking at the size of the VO fifo size to
determine the size of the A-MSDU which led to a lower throughput.

Note that for those devices the only user of the AC -> fifo mapping is
the size limitation of A-MSDU.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240218194912.da336ca2fa0a.I73e44d5fc474ebb6f275b9008950e59c012f33b2@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>