ALSA: oxygen: handle CD input configuration with a flag

There are more models without a CD input than with one, so handle this
explicitly with a device_config flag to avoid having to define a control
filter callback to filter it out.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>