mac80211: handle no-preauth flag for control port

This patch adds support for disabling pre-auth rx over the nl80211 control
port for mac80211.

Signed-off-by: Markus Theil <markus.theil@tu-ilmenau.de>
Link: https://lore.kernel.org/r/20200312091055.54257-3-markus.theil@tu-ilmenau.de


[fix indentation slightly, squash feature enablement]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>