[PATCH] driver core: safely unbind drivers for devices not on a bus

This patch (as667) changes the __device_release_driver() routine to
prevent it from crashing when it runs across a device not on any bus.
This seems logical, inasmuch as the corresponding bus_add_device()
routine has an explicit check allowing it to accept such devices.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>