mac80211: simplify AP_VLAN handling

Setting keys and updating TKIP keys must use the
BSS sdata (not AP_VLAN), so we translate. Move
the translation into driver-ops wrappers instead
of having it inline in the code to simplify the
normal code flow.

The same can be done for sta_add/remove which
already does the translation in the wrapper.

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