cfg80211: emulate connect with auth/assoc

This adds code to cfg80211 so that drivers (mac80211 right
now) that don't implement connect but rather auth/assoc can
still be used with the nl80211 connect command. This will
also be necessary for the wext compat code.

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