mac80211: allow bigger A-MSDU sizes in VHT, even if HT is limited

Some APs (e.g. Asus RT-AC88U) have been observed to report an HT MSDU size
limit of 3839 and a VHT limit of 7991. These APs can handle bigger frames
than 3839 bytes just fine, so we should remove the VHT limit based on the
HT capabilities. This improves tx throughput.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20200916164611.8022-1-nbd@nbd.name


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