iwlwifi: add workaround to disable wide channels in 5GHz

The OTP in some SKUs have erroneously allowed 40MHz and 80MHz channels
in the 5.2GHz band.  The firmware has been modified to not allow this
in those SKUs, so the driver needs to do the same otherwise the
firmware will assert when we try to use it.

Cc: stable@vger.kernel.org
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>