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_pcmcia.c b/drivers/ata/pata_pcmcia.c
index 2e206c5..3d39f9d 100644
--- a/drivers/ata/pata_pcmcia.c
+++ b/drivers/ata/pata_pcmcia.c
@@ -133,14 +133,14 @@
 
 static struct ata_port_operations pcmcia_port_ops = {
 	.inherits	= &ata_sff_port_ops,
-	.data_xfer	= ata_sff_data_xfer_noirq,
+	.sff_data_xfer	= ata_sff_data_xfer_noirq,
 	.cable_detect	= ata_cable_40wire,
 	.set_mode	= pcmcia_set_mode,
 };
 
 static struct ata_port_operations pcmcia_8bit_port_ops = {
 	.inherits	= &ata_sff_port_ops,
-	.data_xfer	= ata_data_xfer_8bit,
+	.sff_data_xfer	= ata_data_xfer_8bit,
 	.cable_detect	= ata_cable_40wire,
 	.set_mode	= pcmcia_set_mode_8bit,
 };