With loadable modules we may get the following during init:

could not initialize VBUS or ID IIO: -517

Let's not print any pointless error messages for deferred probe.
Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>