In walk_up_proc() we have several sanity checks that should only trip if
the programmer made a mistake.  Convert these to ASSERT()'s instead of
BUG_ON()'s.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>