WPS: Use separate list of NFC Password Tokens in the Registrar

WPS: Use separate list of NFC Password Tokens in the Registrar

This adds a cleaner mechanism for handling NFC Password Tokens in the
WPS Registrar. There could be more than one active NFC Password Token in
use and as such, a list of tokens needs to be maintained. The old
WPS_OOB interface is still using the old mechanism that supports only a
single active NFC Password Token.

Signed-hostap: Jouni Malinen <j@w1.fi>