iwlwifi: disable disconnected antenna for advanced bt coex

Disconnected antenna algorithm is used to find out which antennas are
disconnected. It should be disabled for devices that support advanced
bluetooth coexist.

Signed-off-by: Shanyu Zhao <shanyu.zhao@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>