ALSA: au88x0: clipping ceiling loop wrong in comment

As is the clipping ceiling loop appears wrong anyways

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>