P2P: Optimize scan frequencies list when re-joining a persistent group

P2P: Optimize scan frequencies list when re-joining a persistent group

When starting a P2P client to re-join a persistent group
(P2P_GROUP_ADD persistent=<id>), it is possible that the P2P GO was
already found in previous scans. Try to get the P2P GO operating
frequency from the scan results list so wpa_supplicant will initially
scan only the P2P GO known operating frequency.

Signed-off-by: Avraham Stern <avraham.stern@intel.com>
Signed-off-by: Ilan Peer <ilan.peer@intel.com>