mac80211: Assign correct TID for local bridged packets

This patch assigns correct TID to frames transmitted between
two stations in the same BSS in AP mode.
The problem is that skb->protocol is not set to ETH_P_IP and it is wrong
to use that field at this stage.
The fix compares the LLC/Protocol headers explicitly to check if the
encapsulated frame is IP frame

Signed-off-by: Guy Cohen <guy.cohen@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>