mac80211: cleanup generic suspend/resume procedures

Since now we disconnect before suspend, various code which save
connection state can now be removed from suspend and resume
procedure. Cleanup on resume side is smaller as ieee80211_reconfig()
is also used for H/W restart.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>