hostapd: Add virt/phy flag for Display/PushButton if needed (WPS 2.0)

hostapd: Add virt/phy flag for Display/PushButton if needed (WPS 2.0)

This seems to be the easiest way of making sure the Config Methods
value is compliant with the WSC 2.0 specification without having
to modify the configuration file. However, this will only add the
virtual flag, so the configuration files should really be updated
to specify values that match the AP design.