[PATCH] USB: Usbcore: Don't try to delete unregistered interfaces

This patch handles a rarely-encountered failure mode in usbcore.  It's
legal for device_add to fail (although now it happens even more rarely
than before since failure to bind a driver is no longer fatal).  So when
we destroy the interfaces in a configuration, we shouldn't try to delete
ones which weren't successfully registered.  Also, failure to register an
interface shouldn't be fatal either -- I think; you may disagree about
this part of the patch.

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