[PATCH] powerpc: Add/remove/update properties in /proc/device-tree

Add support to the proc_device_tree file for removing
and updating properties.  Remove just removes the
proc file, update changes the data pointer within
the proc file.  The remainder of the device-tree
changes occur elsewhere.

Signed-off-by: Dave Boutcher <sleddog@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>