mac80211: fix IEEE80211_SDATA_DISCONNECT_RESUME

Since commit 12e7f517029dad819c45eca9ca01fdb9ba57616b,
IEEE80211_SDATA_DISCONNECT_RESUME no longer worked as
it would simply never be tested. Restore a bit of the
code removed there and in 9b7d72c1041ec5b20b24af487a9
to make it work again.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --cc net/mac80211/ieee80211_i.h
Simple merge

diff --cc net/mac80211/mlme.c
Simple merge

diff --cc net/mac80211/util.c
Simple merge