libata: rename SFF port ops

Add sff_ prefix to SFF specific port ops.

This rename is in preparation of separating SFF support out of libata
core layer.  This patch strictly renames ops and doesn't introduce any
behavior difference.

Signed-off-by: Tejun Heo <htejun@gmail.com>
diff --git a/drivers/ata/pata_icside.c b/drivers/ata/pata_icside.c
index 52de9f9..1713843 100644
--- a/drivers/ata/pata_icside.c
+++ b/drivers/ata/pata_icside.c
@@ -250,7 +250,7 @@
 	set_dma_mode(state->dma, write ? DMA_MODE_WRITE : DMA_MODE_READ);
 
 	/* issue r/w command */
-	ap->ops->exec_command(ap, &qc->tf);
+	ap->ops->sff_exec_command(ap, &qc->tf);
 }
 
 static void pata_icside_bmdma_start(struct ata_queued_cmd *qc)
@@ -336,7 +336,7 @@
 	.inherits		= &ata_sff_port_ops,
 	/* no need to build any PRD tables for DMA */
 	.qc_prep		= ata_noop_qc_prep,
-	.data_xfer		= ata_sff_data_xfer_noirq,
+	.sff_data_xfer		= ata_sff_data_xfer_noirq,
 	.bmdma_setup		= pata_icside_bmdma_setup,
 	.bmdma_start		= pata_icside_bmdma_start,
 	.bmdma_stop		= pata_icside_bmdma_stop,