pata_marvell: Cable and reset fixes

There are two changes here. Firstly we switch to a cable detect method,
secondly the old code forgot to call ata_std_prereset() but somehow
managed to work anyway. Fix the missing call.

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