ARM: k2g: setup PRU ethernet MAC addresses

PRU ethernet MAC address range is present in the
board EEPROM. Parse it and setup eth?addr
environment variables.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>