[POWERPC] powerpc: remove references to the obsolete linux,platform property

Remove references to the linux,platform property from
booting-without-of.txt since it is obsolete.
Signed-off-by: NStuart Yoder <stuart.yoder@freescale.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Documentation/powerpc/booting-without-of.txt

@@ -509,7 +509,6 @@ looks like in practice.
       o chosen
         |- name = "chosen"
         |- bootargs = "root=/dev/sda2"
-        |- linux,platform = <00000600>
         |- linux,phandle = <4>
 
 This tree is almost a minimal tree. It pretty much contains the
@@ -733,8 +732,7 @@ address which can extend beyond that limit.
       that typically get driven by the same platform code in the
       kernel, you would use a different "model" property but put a
       value in "compatible". The kernel doesn't directly use that
-      value (see /chosen/linux,platform for how the kernel chooses a
-      platform type) but it is generally useful.
+      value but it is generally useful.
 
   The root node is also generally where you add additional properties
   specific to your board like the serial number if any, that sort of
@@ -842,11 +840,6 @@ address which can extend beyond that limit.
   the prom_init() trampoline when booting with an OF client interface,
   but that you have to provide yourself when using the flattened format.
 
-  Required properties:
-
-    - linux,platform : This is your platform number as assigned by the
-      architecture maintainers
-
   Recommended properties:
 
     - bootargs : This zero-terminated string is passed as the kernel