iwlwifi: rate scale restructure toggle_antenna functions

This patch add support for toggeling of A/B/C and AB/BC/AC
antennas

Signed-off-by: Guy Cohen <guy.cohen@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>