pata_sch: use ata_pci_sff_init_one()

pata_sch is standard SFF.  No reason to open code init.  Use
ata_pci_sff_init_one() instead.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>