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/mips/au1xxx-ide.c b/drivers/ide/mips/au1xxx-ide.c
index 0d5e4c6..b04db9f 100644
--- a/drivers/ide/mips/au1xxx-ide.c
+++ b/drivers/ide/mips/au1xxx-ide.c
@@ -175,13 +175,11 @@
 	ide_config_drive_speed(drive, speed);
 }
 
-static int auide_tune_chipset (ide_drive_t *drive, u8 speed)
+static int auide_tune_chipset(ide_drive_t *drive, const u8 speed)
 {
 	int mem_sttime;
 	int mem_stcfg;
 
-	speed = ide_rate_filter(drive, speed);
-
 	mem_sttime = 0;
 	mem_stcfg  = au_readl(MEM_STCFG2);