wifi: iwlwifi: mvm: use EHT maximum MPDU length on 2.4 GHz

On 2.4 GHz there's no VHT, so EHT defines its own bits for
the maximum MPDU length. Use them when telling firmware
about the maximum.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230620125813.fd5322bb48a4.Ic471045f83229ceaacce25edcf992d3ce2c75de5@changeid


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