powerpc: 83xx: pci: Remove need for get_immrbase from mpc83xx_add_bridge.

Modify mpc83xx_add_bridge to get config space register base address from
the device tree instead of immr + hardcoded offset.

83xx pci nodes have this change:
    register properties now contain two address length tuples:
	First is the pci bridge register base, this has always been there.
	Second is the config base, this is new.

This is documented in dts-bindings/fsl/83xx-512x-pci.txt

The changes accomplish these things:
    mpc83xx_add_bridge no longer needs to call get_immrbase
    it uses hard coded addresses if the second register value is missing

Signed-off-by: John Rigby <jrigby@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/boot/dts/mpc836x_rdk.dts

@@ -409,7 +409,8 @@
 		#interrupt-cells = <1>;
 		device_type = "pci";
 		compatible = "fsl,mpc8360-pci", "fsl,mpc8349-pci";
-		reg = <0xe0008500 0x100>;
+		reg = <0xe0008500 0x100		/* internal registers */
+		       0xe0008300 0x8>;		/* config space access registers */
 		ranges = <0x02000000 0 0x90000000 0x90000000 0 0x10000000
 			  0x42000000 0 0x80000000 0x80000000 0 0x10000000
 			  0x01000000 0 0xe0300000 0xe0300000 0 0x00100000>;