libata-sff: rename ap->ops->drain_fifo() to sff_drain_fifo()

->drain_fifo() is SFF specific.  Rename and relocate it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 45a547e..19f716e 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -856,13 +856,12 @@
 	void (*sff_irq_on)(struct ata_port *);
 	bool (*sff_irq_check)(struct ata_port *);
 	void (*sff_irq_clear)(struct ata_port *);
+	void (*sff_drain_fifo)(struct ata_queued_cmd *qc);
 
 	void (*bmdma_setup)(struct ata_queued_cmd *qc);
 	void (*bmdma_start)(struct ata_queued_cmd *qc);
 	void (*bmdma_stop)(struct ata_queued_cmd *qc);
 	u8   (*bmdma_status)(struct ata_port *ap);
-
-	void (*drain_fifo)(struct ata_queued_cmd *qc);
 #endif /* CONFIG_ATA_SFF */
 
 	ssize_t (*em_show)(struct ata_port *ap, char *buf);