libata-sff: kill unused prototype and make ata_dev_select() static

ata_irq_on() was renamed to ata_sff_irq_on() and exported a while ago
but prototype for the original function lingered in
drivers/ata/libata.h.  Kill it.  Also, ata_dev_select() is only used
inside drivers/ata/libata-sff.c.  Make it static.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
index a4700af..d5dd88d 100644
--- a/drivers/ata/libata-sff.c
+++ b/drivers/ata/libata-sff.c
@@ -511,7 +511,7 @@
  *	LOCKING:
  *	caller.
  */
-void ata_dev_select(struct ata_port *ap, unsigned int device,
+static void ata_dev_select(struct ata_port *ap, unsigned int device,
 			   unsigned int wait, unsigned int can_sleep)
 {
 	if (ata_msg_probe(ap))