The WS-AP3710i does not correctly expose its label-mac on eth0 anymore
since the change to simpleLoader.
Fix this by obtaining the label-mac from the U-Boot environment.
Signed-off-by: David Bauer <mail@david-bauer.net>
(cherry picked from commit e321e70ddcd82e0b4a5ad695b83a88d44cde02b4)