ALSA: virtuoso: add HDMI enable switch for HDAV1.3

The GPIO bit that enables analog output on the Xonar HDAV1.3 also
disables the HDMI audio output, so we better add a switch for it.
Hopefully, this is sufficient to make the HDMI output work.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/oxygen/xonar.h b/sound/pci/oxygen/xonar.h
index b35343b..0434c20 100644
--- a/sound/pci/oxygen/xonar.h
+++ b/sound/pci/oxygen/xonar.h
@@ -24,6 +24,8 @@
 void xonar_init_cs53x1(struct oxygen *chip);
 void xonar_set_cs53x1_params(struct oxygen *chip,
 			     struct snd_pcm_hw_params *params);
+
+#define XONAR_GPIO_BIT_INVERT	(1 << 16)
 int xonar_gpio_bit_switch_get(struct snd_kcontrol *ctl,
 			      struct snd_ctl_elem_value *value);
 int xonar_gpio_bit_switch_put(struct snd_kcontrol *ctl,