mac80211: simplify scan state machine

Attempting to micro-optimise the scan by going
fully live again when scanning the operating
channel just made the code extremely complex
and has little gain in most use cases. Remove
all that code and simplify the state machine
again.

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