libpayload: Add check for failure in usb_attach_device()

This adds a simple check if a device is really configured before
returning it's address to the usb hub driver who wants to attach it.

Change-Id: I6fea140217c3e7468cc48ef7c3cbf2be8d11f47a
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: http://review.coreboot.org/1131
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
1 file changed