pata_serverworks: Fix cable types and cosmetics

Minor tidying up. Only real change is to return UNK not 80 wire when we
don't know the cable type. This didn't use to matter but with Tejun's
reworking of cable detection it may.

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