iwlwifi: HT IE in probe request clean up

This patch cleans up the scan flow. This patch cleans up the insertion of
the HT IE in the probe request.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>