ide: move ide_rate_filter() calls to the upper layer (take 2)

* Move ide_rate_filter() calls from host drivers to IDE core.

* Make ide_rate_filter() static.

* Make 'speed' argument of ->speedproc const.

v2:
* Fix it8213_tune_chipset() comment.

There should be no functionality changes caused by this patch.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/pci/sc1200.c b/drivers/ide/pci/sc1200.c
index 9bdc969..059071c 100644
--- a/drivers/ide/pci/sc1200.c
+++ b/drivers/ide/pci/sc1200.c
@@ -138,7 +138,7 @@
 	return mask;
 }
 
-static int sc1200_tune_chipset(ide_drive_t *drive, u8 mode)
+static int sc1200_tune_chipset(ide_drive_t *drive, const u8 mode)
 {
 	ide_hwif_t		*hwif = HWIF(drive);
 	int			unit = drive->select.b.unit;
@@ -146,8 +146,6 @@
 	unsigned short		pci_clock;
 	unsigned int		basereg = hwif->channel ? 0x50 : 0x40;
 
-	mode = ide_rate_filter(drive, mode);
-
 	/*
 	 * Tell the drive to switch to the new mode; abort on failure.
 	 */