ata_sff_irq_clear() is BMDMA specific. Rename it to
ata_bmdma_irq_clear(), move it to ata_bmdma_port_ops and make
->sff_irq_clear() optional.
Note: ata_bmdma_irq_clear() is actually only needed by ata_piix and
possibly by sata_sil. This should be moved to respective low
level drivers later.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>