mac80211: simplify mesh frame queue mapping and QoS

We only need to set the skb queue twice:

1. by the netdev, on local TX.
2. when forwarding a mesh frame.

We only need to set the qos header twice:

1. by mac80211, on local TX.
2. when putting a frame on the mpath->frame_queue

We also don't need the RA in order to set the proper queue mapping since
all mesh STAs are QoS, indicate this and do it once when the frame is
received. Also fixes an issue where the QoS header and queue mapping was not
set for unicast forwarded frames.

Signed-off-by: Javier Cardona <javier@cozybit.com>
Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>