[ALSA] oxygen: simplify DAC volume initialization

When initializing the DAC volume registers, we can just use the generic
volume update functions instead of setting the registers manually.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --cc sound/pci/oxygen/hifier.c
Simple merge

diff --cc sound/pci/oxygen/oxygen.c
Simple merge

diff --cc sound/pci/oxygen/virtuoso.c
Simple merge