usb: hub: Reduce warning to notice on power loss

Currently we warn the user when the root hub lost power after resume,
but the user cannot do anything about it so it should probably be a
notice.

This will reduce the noise in the console during suspend and resume,
which is already quite significant in many systems.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>