FT: Allow wpa_supplicant to be configured to prepend PMKR1Name

FT: Allow wpa_supplicant to be configured to prepend PMKR1Name

The standard is somewhat unclear on whether the PMKIDs used in
(Re)Association Request frame (i.e., potential PMKIDs that could be used
for PMKSA caching during the initial mobility domain association) are to
be retained or removed when generating EAPOL-Key msg 2/4.

wpa_supplicant has replaced the PMKID List contents from (Re)Association
Request frame with PMKR1Name when generating EAPOL-Key msg 2/4 for FT.
Allow it to be configured (ft_prepend_pmkid=1) to prepend the PMKR1Name
without removing the PMKIDs from (Re)Association Request frame.

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