Add an EAPOL payload length workaround for a WPS implementation

Add an EAPOL payload length workaround for a WPS implementation

Buffalo WHR-G125 Ver.1.47 seems to send EAP-WPS packets with too short
EAPOL header length field (14 octets regardless of EAP frame length).
This is fixed in firmware Ver.1.49, but the broken version is included
in many deployed APs. As a workaround, fix the EAPOL header based on the
correct length in the EAP packet. This workaround can be disabled with
eap_workaround=0 option in the network configuration.