libata: Early CFA adapters are not required to support mode setting

If we are doing a PIO setup for a CFA card and it blows up with a device
error then assume it is an older CFA card which doesn't support this
rather than failing the device out of existance.

Stands seperate to the quieting patch but that is obviously useful with
this change.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>