RDU1 stores various configuration parameters, including FEC's MAC
address, in a configuration blob that can be located in on of three
places: SPI NOR, RAVE SP EEPROM or Microwire EEPROM.

This patch add an initcall to load those configuration variables from
a valid source (CRC8 checked) as well as expose then as "config_<var>"
environment variables.

This patch also adds appropriate code to register MAC address obtained
from config blob.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>