Add csa_settings struct which holds parameters for CSA. Change driver
interface for switch_channel(), so that it will receive this struct and
not only the new frequency as it was before. This allows wpa_supplicant
to provide all the required parameters (beacons, proberesp, assocresp,
CSA IE) which are required by cfg80211 implementation.
Signed-hostap: Andrei Otcheretianski <andrei.otcheretianski@intel.com>