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>
diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
index 114fa81..942aeba 100644
--- a/drivers/ata/libata-sff.c
+++ b/drivers/ata/libata-sff.c
@@ -827,7 +827,8 @@
  */
 void ata_bmdma_post_internal_cmd(struct ata_queued_cmd *qc)
 {
-	ata_bmdma_stop(qc);
+	if (qc->ap->ioaddr.bmdma_addr)
+		ata_bmdma_stop(qc);
 }
 
 #ifdef CONFIG_PCI