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_legacy.c b/drivers/ata/pata_legacy.c
index f13f10a..7af4b29 100644
--- a/drivers/ata/pata_legacy.c
+++ b/drivers/ata/pata_legacy.c
@@ -226,12 +226,12 @@
 
 static struct ata_port_operations simple_port_ops = {
 	.inherits	= &legacy_base_port_ops,
-	.data_xfer	= ata_sff_data_xfer_noirq,
+	.sff_data_xfer	= ata_sff_data_xfer_noirq,
 };
 
 static struct ata_port_operations legacy_port_ops = {
 	.inherits	= &legacy_base_port_ops,
-	.data_xfer	= ata_sff_data_xfer_noirq,
+	.sff_data_xfer	= ata_sff_data_xfer_noirq,
 	.set_mode	= legacy_set_mode,
 };
 
@@ -325,7 +325,7 @@
 static struct ata_port_operations pdc20230_port_ops = {
 	.inherits	= &legacy_base_port_ops,
 	.set_piomode	= pdc20230_set_piomode,
-	.data_xfer	= pdc_data_xfer_vlb,
+	.sff_data_xfer	= pdc_data_xfer_vlb,
 };
 
 /*
@@ -775,19 +775,19 @@
 	.inherits	= &legacy_base_port_ops,
 	.set_piomode	= qdi6500_set_piomode,
 	.qc_issue	= qdi_qc_issue,
-	.data_xfer	= vlb32_data_xfer,
+	.sff_data_xfer	= vlb32_data_xfer,
 };
 
 static struct ata_port_operations qdi6580_port_ops = {
 	.inherits	= &legacy_base_port_ops,
 	.set_piomode	= qdi6580_set_piomode,
-	.data_xfer	= vlb32_data_xfer,
+	.sff_data_xfer	= vlb32_data_xfer,
 };
 
 static struct ata_port_operations qdi6580dp_port_ops = {
 	.inherits	= &legacy_base_port_ops,
 	.set_piomode	= qdi6580dp_set_piomode,
-	.data_xfer	= vlb32_data_xfer,
+	.sff_data_xfer	= vlb32_data_xfer,
 };
 
 static DEFINE_SPINLOCK(winbond_lock);
@@ -858,7 +858,7 @@
 static struct ata_port_operations winbond_port_ops = {
 	.inherits	= &legacy_base_port_ops,
 	.set_piomode	= winbond_set_piomode,
-	.data_xfer	= vlb32_data_xfer,
+	.sff_data_xfer	= vlb32_data_xfer,
 };
 
 static struct legacy_controller controllers[] = {