iwlwifi: mvm: add channel 14 to the low band list

in family 8000: additional channel 14 added to the low
band list. now the number of channels in the low band
is 15.

Signed-off-by: Eran Harary <eran.harary@intel.com>
Reviewed-by: Dor Shaish <dor.shaish@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>