ide: switch set_xfer_rate() to use REQ_TYPE_ATA_TASKFILE requests

Based on the earlier work by Tejun Heo.

Switch set_xfer_rate() to use REQ_TYPE_ATA_TASKFILE requests
and make ide_wait_cmd() static.

There should be no functionality changes caused by this patch.

Cc: Tejun Heo <htejun@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/ide-proc.c b/drivers/ide/ide-proc.c
index a4007d3..aa663e7 100644
--- a/drivers/ide/ide-proc.c
+++ b/drivers/ide/ide-proc.c
@@ -346,14 +346,20 @@
 
 static int set_xfer_rate (ide_drive_t *drive, int arg)
 {
+	ide_task_t task;
 	int err;
 
 	if (arg < 0 || arg > 70)
 		return -EINVAL;
 
-	err = ide_wait_cmd(drive,
-			WIN_SETFEATURES, (u8) arg,
-			SETFEATURES_XFER, 0, NULL);
+	memset(&task, 0, sizeof(task));
+	task.tf.command = WIN_SETFEATURES;
+	task.tf.feature = SETFEATURES_XFER;
+	task.tf.nsect   = (u8)arg;
+	task.tf_flags = IDE_TFLAG_OUT_FEATURE | IDE_TFLAG_OUT_NSECT |
+			IDE_TFLAG_IN_NSECT;
+
+	err = ide_no_data_taskfile(drive, &task);
 
 	if (!err && arg) {
 		ide_set_xfer_rate(drive, (u8) arg);