wifi: iwlwifi: mvm: support flush on AP interfaces

Support TX flush on AP interfaces so that we will do a
proper flush for frames on the queue before keys are
removed.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230816104355.f4b749b91ec2.Ia8381bd4f7d47592e74387c564739798a01c4049@changeid


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