x86, mrst, pci: return 0 for non-present pci bars

Moorestown PCI code has special handling of devices with fixed BARs. In
case of BAR sizing writes, we need to update the fake PCI MMCFG space with real
size decode value.

When a BAR is not present, we need to return 0 instead of ~0. ~0 will be
treated as device error per bugzilla 12006.
Signed-off-by: NJacob Pan <jacob.jun.pan@linux.intel.com>
LKML-Reference: <1273873281-17489-2-git-send-email-jacob.jun.pan@linux.intel.com>
Acked-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

arch/x86/pci/mrst.c

@@ -109,7 +109,7 @@ static int pci_device_update_fixed(struct pci_bus *bus, unsigned int devfn,
 			decode++;
 			decode = ~(decode - 1);
 		} else {
-			decode = ~0;
+			decode = 0;
 		}
 
 		/*