mac80211: make master iface not wireless

There's no need to register the master netdev with cfg80211,
in fact, this is quite dangerous and lead to having to add
checks for the master interface all over the config handlers.
This patch removes the "ieee80211_ptr" from the master iface
in favour of having a small netdev_priv() associated with
the master interface that stores the ieee80211_local pointer.
Because of this, a lot of code in the configuration handlers
can go away. To make this patch easier to verify I have also
removed a number of wiphy_priv() calls in favour of getting
the sdata first and then the local pointer from that.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>