libata-sff: Don't call bmdma_stop on non DMA capable controllers

Fixes bogus accesses to ports 0-15 with a non DMA capable controller.
This I think should go in for 2.6.20
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/ata/libata-sff.c

@@ -827,6 +827,7 @@ void ata_bmdma_error_handler(struct ata_port *ap)
  */
 void ata_bmdma_post_internal_cmd(struct ata_queued_cmd *qc)
 {
+	if (qc->ap->ioaddr.bmdma_addr)
 		ata_bmdma_stop(qc);
 }