This reverts commit 
dda444d52496aa8ddc501561bca580f1374a96a9.
Channel switching code has been reworked and
improved significantly since the time original
locking issues were found.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
        int i;
        u16 ifmodes = wiphy->interface_modes;
 
-       /*
-        * There are major locking problems in nl80211/mac80211 for CSA,
-        * disable for all drivers until this has been reworked.
-        */
-       wiphy->flags &= ~WIPHY_FLAG_HAS_CHANNEL_SWITCH;
-
 #ifdef CONFIG_PM
        if (WARN_ON(wiphy->wowlan &&
                    (wiphy->wowlan->flags & WIPHY_WOWLAN_GTK_REKEY_FAILURE) &&