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/ide-xfer-mode.c b/drivers/ide/ide-xfer-mode.c
index af44be9..0b47ca1 100644
--- a/drivers/ide/ide-xfer-mode.c
+++ b/drivers/ide/ide-xfer-mode.c
@@ -107,6 +107,12 @@
 }
 EXPORT_SYMBOL_GPL(ide_get_best_pio_mode);
 
+int ide_pio_need_iordy(ide_drive_t *drive, const u8 pio)
+{
+	return ata_id_pio_need_iordy(drive->id, pio);
+}
+EXPORT_SYMBOL_GPL(ide_pio_need_iordy);
+
 int ide_set_pio_mode(ide_drive_t *drive, const u8 mode)
 {
 	ide_hwif_t *hwif = drive->hwif;