Instead of allocating sk_buff for a mere 16-byte
tx fragment list buffer use headroom of the
original msdu sk_buff.
This decreases CPU cache pressure and improves
performance.
Measured improvement on AP135 is 560mbps ->
590mbps of UDP TX briding traffic.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>