mac80211: fix mgmt frame accounting

The recent change to processing action frames from
the management frame queue had already broken action
frame accounting, and my rework didn't help either.
So add back accounting and simplify the code with a
label rather than duplicating it, and also add
accounting for management frames.

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