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>
diff --git a/sound/pci/oxygen/oxygen.h b/sound/pci/oxygen/oxygen.h
index a3409ed..7d5222c 100644
--- a/sound/pci/oxygen/oxygen.h
+++ b/sound/pci/oxygen/oxygen.h
@@ -34,6 +34,7 @@
      /* CAPTURE_3_FROM_I2S_3		not implemented */
 #define MIDI_OUTPUT		0x0800
 #define MIDI_INPUT		0x1000
+#define AC97_CD_INPUT		0x2000
 
 enum {
 	CONTROL_SPDIF_PCM,