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/include/linux/ide.h b/include/linux/ide.h
index cdb29b6..8c7f5e5 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -1514,6 +1514,7 @@
 int ide_scan_pio_blacklist(char *);
 const char *ide_xfer_verbose(u8);
 u8 ide_get_best_pio_mode(ide_drive_t *, u8, u8);
+int ide_pio_need_iordy(ide_drive_t *, const u8);
 int ide_set_pio_mode(ide_drive_t *, u8);
 int ide_set_dma_mode(ide_drive_t *, u8);
 void ide_set_pio(ide_drive_t *, u8);