buildroot

hostapd: enable interworking and enhance

Enable IEEE 802.11u (interworking).
Also enable new supported EAP methods.
Switch from echo to sed where possible for a cleaner .config output

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>