au1000: distinguish different models and set correct MAC-address

The target au1000 has at least 2 different models, the
'InternetBox' and the 'MeshCube' which look very similar
from the kernel point of view but are totally different
devices which base on the same design. Populating /tmp/sysinfo
now. The 1st one has an issue which leads to a random
mac-address after each boot which is corrected now via
reading the bootloader-env. The real fix would be
converting to DTS, this is only a workaround now.

Signed-off-by: Bastian Bittorf <bittorf@bluebottle.com>

SVN-Revision: 43626