set_ap_wps_ie() is not used to set WPS IE for both Beacon and Probe
Response frames with a single call. In addition, struct wpabuf is used
instead of separate u8* and length fields. This avoids duplicated
allocation of the IEs and simplifies code in general.
It would be bettet to avoid including driver_i.h, i.e., direct driver
operation calls from hostapd components. This is an initial step in
that direction for WPS IE updates.
