iwlwifi: kill iwl3945_scan_cancel and iwl3945_scan_cancel_timeout

This patch removes iwl3945_scan_cancel and iwl3945_scan_cancel_timeout
because iwl_scan_cancel iwl_scan_cancel_timeout are just same.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>