x86/pci: Intel ioh bus num reg accessing fix

It is above 0x100 (PCI-Express extended register space), so if mmconf
is not enable, we can't access it.

[ hpa: changed the bound from 0x200 to 0x120, which is the tight
  bound. ]

Reported-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <1261525263-13763-3-git-send-email-yinghai@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>