P2P: Add support for preferred channel list

P2P: Add support for preferred channel list

p2p_pref_chan configuration parameter can now be used to set the
list of preferred channel for P2P GO Negotiation. This will be used
in the priority order if the peer does not support the channel we
are trying to use as the GO (configured operating channel or the
best 2.4 GHz/5 GHz channel) for the case where a forced channel is
not used.

p2p_pref_chan=<op class:channel>,...

For example:
p2p_pref_chan=81:1,81:2,81:3,81:4,81:5,81:6

This would configure 2.4 GHz channels 1-6 as the preferred ones with
channel 1 the most preferred option.

These configuration parameters can be set in wpa_supplicant.conf and
dynamically updated with "wpa_cli set <param> <value>".

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