ht6560b can only do up to PIO mode 4

According to the datasheet, ht6560b only supports up to PIO mode 4.

[bart: manually ported it over 2.6.25-rc2]
Signed-off-by: NJan Evert van Grootheest <janevert@caiway.nl>
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/legacy/ht6560b.c

@@ -323,7 +323,7 @@ static const struct ide_port_info ht6560b_port_info __initdata = {
 				  IDE_HFLAG_NO_DMA |
 				  IDE_HFLAG_NO_AUTOTUNE |
 				  IDE_HFLAG_ABUSE_PREFETCH,
-	.pio_mask		= ATA_PIO5,
+	.pio_mask		= ATA_PIO4,
 };
 
 static int __init ht6560b_init(void)