mac80211: add spectrum capabilities

This patch add spectrum capability and required information
elements to association request providing AP has requested it and
it is supported by the driver

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Assaf Krauss <assaf.krauss@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>