Use ClientID instead of DUID in dhcpcd requests (#18)

- With DUID, new DHCP leases would be issued upon reboot when paired with DHCP servers that respect DUID, instead of reusing the existing DHCP lease.
- The MiSTer installation process now generates a random hardware address, so DUID is unnecessary. Including DUID results in wasted leases within a DHCP scope, and can also lead to DNS resolution issues when accessing the device.
- More details
  - MiSTer-devel/Linux-Kernel_MiSTer#29 (comment)
  - MiSTer-devel/Linux-Kernel_MiSTer#29 (comment)
  - https://misterfpga.org/viewtopic.php?p=74311#p74311

create_img.sh

@@ -70,6 +70,7 @@ mount -o remount,rw /
 __EOF__
 echo -n $(date +%y%m%d) > ${DSTDIR}/MiSTer.version
 sed 's/#hostname/hostname/g' -i ${DSTDIR}/etc/dhcpcd.conf
+sed -e 's/^#clientid/clientid/' -e 's/^duid/#duid/' -i ${DSTDIR}/etc/dhcpcd.conf
 
 echo "Fixing permissions..."
 chown -R root:root ${DSTDIR} || exit 0