uboot-imx

smc911x: write back the manually set MAC address

If the MAX address is given by the environment, write it back to the
hardware.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>