ALSA: oxygen: Fix right channel of capture volume mixer

There was a typo in oxygen mixer code that didn't update the right
channel value properly for the capture volume.  Let's fix it.

This trivial fix was originally reported on Bugzilla.

Fixes: a3601560 ("[ALSA] oxygen: add front panel controls")
Cc: <stable@vger.kernel.org>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=156561
Link: https://lore.kernel.org/r/20240112111023.6208-1-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>