According to the `RFC8415` the length of the DUID is at least 1 octet up to 128 octets. Now a user can choose buffer length without the need for source code modification. Signed-off-by: Marcin Gasiorek <marcin.gasiorek@nordicsemi.no>
For consistency with DHCPv4. Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>