P2P: Allow the avoid channels for P2P discovery/negotiation

P2P: Allow the avoid channels for P2P discovery/negotiation

The avoid channels are notified through
QCA_NL80211_VENDOR_SUBCMD_AVOID_FREQUENCY allow minimal traffic, so
enhance the P2P behavior accordingly by considering these avoid
frequencies for P2P discovery/negotiation as long as they are not in
disallowed frequencies list.

Additionally, do not return failure when none of social channels are
available as operation channel, rather, mark the op_channel/op_reg_class
to 0 as this would anyway get selected during the group formation in
p2p_prepare_channel.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>