8390/etherh: convert to ethtool_{get, set}_link_ksettings

This is the last in-tree driver using the old {get,set}_settings API.

Note: this is only build tested. I don't have the hardware at hand; as it's
10Mb/s half duplex device and driver can be built only for one subplatform
of 32-bit ARM (Acorn RiscPC), it may be difficult to find someone who does.

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>