Now that SFF and BMDMA are completely separate, sata_qstor and
pata_octeon_cf which inherit from ata_sff_port_ops don't need to worry
about BMDMA ops being called.  Kill the dummy BMDMA ops.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>