Even though IPv6 support for hostapd RADIUS server is implemented
(flag `-6`), it's not possible to enable it from configuration.
This commit adds this option and adapts init script.
Signed-off-by: Dávid Benko <davidbenko@davidbenko.dev>
Link: https://github.com/openwrt/openwrt/pull/18089
Signed-off-by: Robert Marko <robimarko@gmail.com>