net: ibm: emac: generate random MAC if not found

net: ibm: emac: generate random MAC if not found

On this Cisco MX60W, u-boot sets the local-mac-address property.
Unfortunately by default, the MAC is wrong and is actually located on a
UBI partition. Which means nvmem needs to be used to grab it.

In the case where that fails, EMAC fails to initialize instead of
generating a random MAC as many other drivers do.

Match behavior with other drivers to have a working ethernet interface.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>