P2P: Add support for automatic channel selection at GO

P2P: Add support for automatic channel selection at GO

The driver wrapper may now indicate the preferred channel (e.g., based
on scan results) on both 2.4 GHz and 5 GHz bands (and an overall best
frequency). When setting up a GO, this preference information is used
to select the operating channel if configuration does not include
hardcoded channel. Similarly, this information can be used during
GO Negotiation to indicate preference for a specific channel based
on current channel conditions.

p2p_group_add command can now use special values (freq=2 and freq=5)
to indicate that the GO is to be started on the specified band.