ASoC: wm8750: Make VREF a VMID instead of OUTPUT widget

Commit 04489eeb02a4 ("ALSA: wm8750: add missing VREF output") added the
previously missing VREF widget. And while adding the widget as OUTPUT widget
silences the error of the missing widget it should have rather been a VMID
widget.

The VREF widget is only used internally as a source for the VREF input of
the Out3 Mux. Selecting that input means that the path should be kept
powered up at the VREF/VMID voltage, but that there is no actual audio
signal. Using a VMID widget will do this, whereas using a OUTPUT widget will
simply cause the path to completely power down.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/sound/soc/codecs/wm8750.c b/sound/soc/codecs/wm8750.c
index 67653a2..d9e2626 100644
--- a/sound/soc/codecs/wm8750.c
+++ b/sound/soc/codecs/wm8750.c
@@ -323,7 +323,7 @@
 	SND_SOC_DAPM_OUTPUT("ROUT2"),
 	SND_SOC_DAPM_OUTPUT("MONO1"),
 	SND_SOC_DAPM_OUTPUT("OUT3"),
-	SND_SOC_DAPM_OUTPUT("VREF"),
+	SND_SOC_DAPM_VMID("VREF"),
 
 	SND_SOC_DAPM_INPUT("LINPUT1"),
 	SND_SOC_DAPM_INPUT("LINPUT2"),