MIPS: PCI: Prevent hang on XLP reg read

Reading PCI extended register at 0x255 on a bridge will hang if there
is no device connected on the link. Make PCI read routine skip this
register.
Signed-off-by: NJayachandran C <jchandra@broadcom.com>
Patchwork: http://patchwork.linux-mips.org/patch/4789/Signed-off-by: NJohn Crispin <blogic@openwrt.org>

arch/mips/pci/pci-xlp.c

@@ -64,8 +64,12 @@ static inline u32 pci_cfg_read_32bit(struct pci_bus *bus, unsigned int devfn,
 	u32 data;
 	u32 *cfgaddr;
 
+	where &= ~3;
+	if (bus->number == 0 && PCI_SLOT(devfn) == 1 && where == 0x954)
+		return 0xffffffff;
+
 	cfgaddr = (u32 *)(pci_config_base +
-			pci_cfg_addr(bus->number, devfn, where & ~3));
+			pci_cfg_addr(bus->number, devfn, where));
 	data = *cfgaddr;
 	return data;
 }