Currently it's not possible to set volume lower than 26% (it just mutes).

Also fixes this warning:

  Warning! Unlikely big volume range (=9472), cval->res is probably wrong.
  [13] FU [PCM Playback Volume] ch = 2, val = -9473/-1/1

, and volume works fine for full range.
Signed-off-by: Federico Cuello <fedux@fedux.com.ar>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>