ti: common: am6: Add support for setting MAC addresses

The AM654x EVM based on the TI K3 family of SoCs has an updated board
detection EEPROM structure that contains a TLV record of dedicated MAC
addresses rather than a range of MAC addresses as it was used on earlier
platforms such as DRA7. Add a basic function that allows us setting up
Ethernet MAC addresses into the U-Boot environment based on the MAC
address record contained in the common TI EEPROM structure.

Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>