[POWERPC] #address-cells & #size-cells properties are not inherited

Fix error in booting-without-of.txt that indicates that a node can inherit
its #address-cells and #size-cells definitions from its parent's parent.
This is not correct.
Signed-off-by: NMark A. Greer <mgreer@mvista.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Documentation/powerpc/booting-without-of.txt

@@ -671,10 +671,10 @@ device or bus to be described by the device tree.
 
 In general, the format of an address for a device is defined by the
 parent bus type, based on the #address-cells and #size-cells
-property. In the absence of such a property, the parent's parent
-values are used, etc... The kernel requires the root node to have
-those properties defining addresses format for devices directly mapped
-on the processor bus.
+properties.  Note that the parent's parent definitions of #address-cells
+and #size-cells are not inhereted so every node with children must specify
+them.  The kernel requires the root node to have those properties defining
+addresses format for devices directly mapped on the processor bus.
 
 Those 2 properties define 'cells' for representing an address and a
 size. A "cell" is a 32-bit number. For example, if both contain 2