pata_pcmcia: Switch to ata_sff_port_start

PCMCIA doesn't use DMA and as this driver is used on many platforms we
don't want it to fail on those that define the DMA alloc API as a NULL
return

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