Interworking: Fix Advertisement Protocol element length limit

The Query Response Length Limit is not allowed to be zero when
this is sent by the AP. Use 0x7F to indicate that the limit is
based on maximum number of GAS fragments.

src/ap/ieee802_11_shared.c

@@ -259,7 +259,7 @@ u8 * hostapd_eid_adv_proto(struct hostapd_data *hapd, u8 *eid)
 
 	*pos++ = WLAN_EID_ADV_PROTO;
 	*pos++ = 2;
-	*pos++ = 0; /* Query Response Length Limit | PAME-BI */
+	*pos++ = 0x7F; /* Query Response Length Limit | PAME-BI */
 	*pos++ = ACCESS_NETWORK_QUERY_PROTOCOL;
 #endif /* CONFIG_INTERWORKING */