wifi: mac80211: work around Cisco AP 9115 VHT MPDU length

Cisco AP module 9115 with FW 17.3 has a bug and sends a too
large maximum MPDU length in the association response
(indicating 12k) that it cannot actually process.

Work around that by taking the minimum between what's in the
association response and the BSS elements (from beacon or
probe response).

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230918140607.d1966a9a532e.I090225babb7cd4d1081ee9acd40e7de7e41c15ae@changeid


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