Fix Ethernet init() return codes

Fix Ethernet init() return codes

Change return values of init() functions in all Ethernet drivers to conform
to the following:

    >=0: Success
    <0:  Failure

All drivers going forward should return 0 on success.  Current drivers that
return 1 on success were left as-is to minimize changes.

Signed-off-by: Ben Warren <[email protected]>
Acked-by: Stefan Roese <[email protected]>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <[email protected]>
Acked-by: Kim Phillips <[email protected]>
Acked-by: Haavard Skinnemoen <[email protected]>
Acked-By: Timur Tabi <[email protected]>