wifi: iwlwifi: mld: enable OMI bandwidth reduction on 6 GHz

wifi: iwlwifi: mld: enable OMI bandwidth reduction on 6 GHz

Due to the iwl_mld_get_chandef_from_chanctx() logic, even after
the OMI handshake to reduce bandwidth the driver wouldn't apply
that to the PHY context, since it always uses the normal, not
the reduced, configuration on 6 GHz (not strictly always, but
OMI will only apply if the original bandwidth is > 80 MHz.) Fix
this by making that selection contingent on AP mode. Refactor
the code a bit to also make it clearer why the min_def isn't
used in that case (for FILS.)

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250309073442.2706cbd0b100.Ic34636b1aee81a140eb690fca8139909a58f8e8b@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>