wifi: iwlwifi: fix iwl_mvm_max_amsdu_size() for MLO

For MLO, we cannot use vif->bss_conf.chandef.chan->band, since
that will lead to a NULL-ptr dereference as bss_conf isn't used.
However, in case of real MLO, we also need to take both LMACs
into account if they exist, since the station might be active
on both LMACs at the same time.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230417113648.3588afc85d79.I11592893bbc191b9548518b8bd782de568a9f848@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>