compulab: eeprom: propagate error value in read_mac_addr()

cl_eeprom_read_mac_addr() doesn't differentiate between success case and
inability to access eeprom. Fix this by propagating the return value of
cl_eeprom_setup().

Cc: Stefano Babic <sbabic@denx.de>
Cc: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
Acked-by: Igor Grinberg <grinberg@compulab.co.il>