net/amd: Remove needless assignment and the extra brank lines

The variable 'err = -ENODEV;' in au1000_probe() is
duplicate, so remove redundant one. And remove the
extra blank lines in the file au1000_eth.c

Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>