hostapd: Expose the tdls_prohibit option to UCI

hostapd: Expose the tdls_prohibit option to UCI

wpa_disable_eapol_key_retries can't prevent attacks against the
Tunneled Direct-Link Setup (TDLS) handshake. Jouni Malinen suggested
that the existing hostapd option tdls_prohibit can be used to further
complicate this possibility at the AP side. tdls_prohibit=1 makes
hostapd advertise that use of TDLS is not allowed in the BSS.

Note: If an attacker manages to lure both TDLS peers into a fake
AP, hiding the tdls_prohibit advertisement from them, it might be
possible to bypass this protection.

Make this option configurable via UCI, but disabled by default.

Signed-off-by: Timo Sigurdsson <public_timo.s@silentcreek.de>