libertas: handle mesh networks in lbs_iface_active()

There was an extra semicolon so the if condition wasn't used.  We
checked "priv->dev" twice instead of "priv->mesh_dev".

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>