The A-MPDU length exponent extension is defined differently in
802.11ax D6.1, align with that.
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210409123755.c2a257d3e2df.I3455245d388c52c61dace7e7958dbed7e807cfb6@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>