Answer
You need to boot into Linux and after Login log in issue the command
fw_setenv ethaddr <desired MAC address> for example: fw_setenv ethaddr AABBCCDDEEFF and reboot You can read out the address previously set with: fw_printenv ethaddr
You need to boot into Linux and after Login log in issue the command
fw_setenv ethaddr <desired MAC address> for example: fw_setenv ethaddr AABBCCDDEEFF and reboot You can read out the address previously set with: fw_printenv ethaddr