hostapd: move reading of rsn_preauth out of auth_type=eap context

rsn_preauth is used outside of "case $auth_type", so if it is set
for an EAP-enabled SSID, it would also be set for the following
non-EAP-enabled SSIDs, because it would not be read again.

Signed-off-by: Reiner Herrmann <reiner@reiner-h.de>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@41012 3c298f89-4303-0410-b956-a3cf2f4a3e73