P2P: Continue scanning specified channel with P2P_FIND freq argument

P2P: Continue scanning specified channel with P2P_FIND freq argument

This makes the "P2P_FIND freq=<MHz>" operation more robust by continuing
to include the specified frequency in the consecutive scan rounds
instead of including it only once in the first scan. In other words, the
first scan is only for the specified frequency just like the previous
behavior, but the following scans include all the social channels and
the specified frequency instead of just the previously used social
channels.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>