iwlwifi: mvm: use defines for SCD_CONFIG_CMD enablement

Due to the addition of another option in the SCD_CONFIG_CMD's
%enable field, change the assignment of this field to use
defines rather than hard-code the value itself.

Signed-off-by: Liad Kaufman <liad.kaufman@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>