ARM: shmobile: Koelsch: enable Ether in defconfig

Enable the Ether driver in 'koelsch_defconfig' along with DHCP autoconfiguration
and NFS root.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>