mac80211: Keep skb->piority for relayed frames in AP mode

mac80211: Keep skb->piority for relayed frames in AP mode

When mac80211 relays a frame from STA1 to STA2 in AP mode it will get
re-classified in the tx path. Unfortunately the frame protocol field
is always set to ETH_P_8023 while the classification only kicks in
for ETH_P_IP. Hence, a high priority frame from STA1 will be send to
STA2 as best effort.

Instead of running classification on the frame just use the same
priority as STA1 did. Do this by adding 256 to the skb->priority
to allow cfg80211_classify8021d to shortcut frame classification.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>