hostapd: Allow rsn_preauth configuration

hostapd: Allow rsn_preauth configuration

Hostapd can allow preauthentication for WPA2-EAP networks when
the interfaces through which preauthentication is allowed are
configured.

Add a new param "rsn_preauth=0/1" to the configuration that enables
or disables preauthentication on the according bridge interface.

Preauthentication for unbridged networks is not considered in this
patch.

Cc: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@24721 3c298f89-4303-0410-b956-a3cf2f4a3e73