iwlwifi: remove support for Narrow Channel (10Mhz)

Setting Narrow Channel bit in the scan command caused the device
not to send probe request on all the channels

Signed-off-by: Guy Cohen <guy.cohen@intel.com>
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>