iwlwifi: support 11h

Set IEEE80211_HW_SPECTRUM_MGMT bit in hw->flags, this tell mac80211
we support spectrum mgmt.

Signed-off-by: Mohamed Abbas <mohamed.abbas@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>