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>

arch/x86/pci/intel_bus.c

@@ -49,6 +49,10 @@ static void __devinit pci_root_bus_res(struct pci_dev *dev)
 	u64 mmioh_base, mmioh_end;
 	int bus_base, bus_end;
 
+	/* some sys doesn't get mmconf enabled */
+	if (dev->cfg_size < 0x120)
+		return;
+
 	if (pci_root_num >= PCI_ROOT_NR) {
 		printk(KERN_DEBUG "intel_bus.c: PCI_ROOT_NR is too small\n");
 		return;