drm/vmwgfx: move the require_exist handling together
Move the render_client hunk for require_exist alongside the rest.
Keeping all the reasons why an existing object is needed, in a single
place makes it easier to follow.
Cc: VMware Graphics <linux-graphics-maintainer@vmware.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Signed-off-by: Emil Velikov <emil.velikov@collabora.com> Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>