[PATCH] libertas: specific mesh scan for mshX interface

With this patch, scanning with mshX interface will only return mesh networks. To
differentiate them, a specific mesh IE in beacons/probe responses is used. This
IE has been introduced in firmware release 5.110.14. Note:

Even though there can be at most a single mesh per channel, this scan might
return several networks in the same channel.

If all nodes in a mesh network are associated to an AP, they won't produce
beacons/probe responses, thus the network will not be listed. This will be fixed
in future firmware releases.

Scan on ethX interface is not filtered, so it will list both mesh and non-mesh
networks.

Signed-off-by: Luis Carlos Cobo <luisca@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>