mac80211: Start implementing QoS support for mesh interfaces

In order to support QoS in mesh, we need to assign queue mapping only
after the next hop has been resolved, both for forwarded and locally
originated frames.  Also, now that this is fixed, remove the XXX comment
in ieee80211_select_queue().

Also, V-Shy Ho reported that the queue mapping was not being applied to
the forwarded frame (fwd_skb instead of skb).  Fixed that as well.

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