P2P: Allow channels to be removed from P2P use

P2P: Allow channels to be removed from P2P use

A list of disallowed frequencies for P2P channel list can now be
configured with P2P_SET disallow_freq. The frequencies (or frequency
pairs) are comma separated. For example:
wpa_cli p2p_set disallow_freq 2462,5000-6000

The allowed P2P channel list is constructed by removing explicitly
disallowed channels from the channel list received from the driver.

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