ide: IORDY handling fixes

Add ide_pio_need_iordy() helper and convert host drivers to use it.

This fixes it8172, it8213, pdc202xx_old, piix, slc90e66 and siimage
host drivers to handle IORDY correctly.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/piix.c b/drivers/ide/piix.c
index 69860de..bf14f39 100644
--- a/drivers/ide/piix.c
+++ b/drivers/ide/piix.c
@@ -98,7 +98,7 @@
 		control |= 1;	/* Programmable timing on */
 	if (drive->media == ide_disk)
 		control |= 4;	/* Prefetch, post write */
-	if (pio > 2)
+	if (ide_pio_need_iordy(drive, pio))
 		control |= 2;	/* IORDY */
 	if (is_slave) {
 		master_data |=  0x4000;