These are necessary to allow writeable mmap of the privcmd node to
succeed without being marked read-only for writenotify purposes. Which
in turn is necessary to allow mappings of foreign guest pages

[ Impact: bugfix: allow writable mappings ]
Signed-off-by: NIan Campbell <ian.campbell@citrix.com>
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>