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/sata_sx4.c b/drivers/ata/sata_sx4.c
index 40be2ff..6107eff 100644
--- a/drivers/ata/sata_sx4.c
+++ b/drivers/ata/sata_sx4.c
@@ -243,18 +243,18 @@
 
 /* TODO: inherit from base port_ops after converting to new EH */
 static struct ata_port_operations pdc_20621_ops = {
-	.tf_load		= pdc_tf_load_mmio,
-	.tf_read		= ata_sff_tf_read,
-	.check_status		= ata_sff_check_status,
-	.exec_command		= pdc_exec_command_mmio,
-	.dev_select		= ata_sff_dev_select,
+	.sff_tf_load		= pdc_tf_load_mmio,
+	.sff_tf_read		= ata_sff_tf_read,
+	.sff_check_status	= ata_sff_check_status,
+	.sff_exec_command	= pdc_exec_command_mmio,
+	.sff_dev_select		= ata_sff_dev_select,
 	.phy_reset		= pdc_20621_phy_reset,
 	.qc_prep		= pdc20621_qc_prep,
 	.qc_issue		= pdc20621_qc_issue,
-	.data_xfer		= ata_sff_data_xfer,
+	.sff_data_xfer		= ata_sff_data_xfer,
 	.eng_timeout		= pdc_eng_timeout,
-	.irq_clear		= pdc20621_irq_clear,
-	.irq_on			= ata_sff_irq_on,
+	.sff_irq_clear		= pdc20621_irq_clear,
+	.sff_irq_on		= ata_sff_irq_on,
 	.port_start		= pdc_port_start,
 };