"ENFORCE_DC" model flag on regions different from EU868

This has not been implemented for regions other than EU868. If you are interested in implementing this for other regions like RU864 (when needed), please see https://github.com/chirpstack/chirpstack-concentratord/blob/master/libconcentratord/src/regulation/standard/etsi_en_300_220.rs for the EU868 implementation.