In the 802.11ad, aka DMG (Dynamic Multi-Gigabit), aka 60Ghz
spec, maximum MSDU size extended to 7920 bytes.
add #define for this.
Signed-off-by: NVladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>