wifi: cfg80211: add a flag to disable wireless extensions

commit be23b2d7

 upstream.

Wireless extensions are already disabled if MLO is enabled,
given that we cannot support MLO there with all the hard-
coded assumptions about BSSID etc.

However, the WiFi7 ecosystem is still stabilizing, and some
devices may need MLO disabled while that happens. In that
case, we might end up with a device that supports wext (but
not MLO) in one kernel, and then breaks wext in the future
(by enabling MLO), which is not desirable.

Add a flag to let such drivers/devices disable wext even if
MLO isn't yet enabled.

Cc: stable@vger.kernel.org
Link: https://msgid.link/20240314110951.b50f1dc4ec21.I656ddd8178eedb49dc5c6c0e70f8ce5807afb54f@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>