smegw01: Read the second MAC address

Currently, only the first MAC address is read from the fuses.

The second MAC address is not read and Linux assigns a random one.

To prevent this behavior, read the second MAC address from the fuses
and store it into the eth1addr environment variable so that it
can be passed to Linux.

Signed-off-by: Fabio Estevam <festevam@denx.de>