cm-t54: add EEPROM support and MAC address handling

cm-t54 Eth MAC address is stored in onboard EEPROM.
Add EEPROM support and setup stored Eth MAC address.

If EEPROM does not contain a valid MAC, then generate it from the
processor ID code (reference code is taken from OMAP5 uEvm board file).

Modify Device Tree blob MAC address field with retrieved data.

Signed-off-by: Dmitry Lifshitz <lifshitz@compulab.co.il>
Acked-by: Igor Grinberg <grinberg@compulab.co.il>