cardbus: limit IO windows to 256 bytes

That's what we've always historically done, and bigger windows seem to
confuse some cardbus bridges. Or something.

Alan reports that this makes the ThinkPad 600x series work properly
again: the 4kB IO window for some reason made IDE DMA not work, which
makes IDE painfully slow even if it works after DMA timeouts.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/pci/setup-bus.c

@@ -40,7 +40,7 @@
  * FIXME: IO should be max 256 bytes.  However, since we may
  * have a P2P bridge below a cardbus bridge, we need 4K.
  */
-#define CARDBUS_IO_SIZE		(4*1024)
+#define CARDBUS_IO_SIZE		(256)
 #define CARDBUS_MEM_SIZE	(32*1024*1024)
 
 static void __devinit