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>
1 file changed