Driver core: Fix cleanup when failing device_add().

 - Don't call cleanup_device_parent() if we didn't call setup_parent().
 - dev->kobj.parent may be NULL when cleanup_device_parent() is called,
   so we need to handle glue_dir == NULL in cleanup_glue_dir().
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>