WPS: Add a workaround for WPA2PSK missing from Enrollee auth flags

WPS: Add a workaround for WPA2PSK missing from Enrollee auth flags

Some deployed implementations seem to advertise incorrect information in
this attribute. A value of 0x1b (WPA2 + WPA + WPAPSK + OPEN, but no
WPA2PSK) has been reported to be used. Add WPA2PSK to the list to avoid
issues with building Credentials that do not use the strongest actually
supported authentication option (that device does support WPA2PSK even
when it does not claim it here).

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