ASoC: dapm: Introduce DAPM_DOUBLE dual channel control type

A DAPM_DOUBLE control type can be used for dual channel mixer input
selectors / mute controls in one register, possibly toggling both
channels together.

The control is meant to be shared by 2 widgets, 1 for each channel,
such that the mixer control exposed to userspace remains a combined
stereo control.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

include/sound/soc-dapm.h

@@ -272,6 +272,11 @@ struct device;
 
 
 /* dapm kcontrol types */
+#define SOC_DAPM_DOUBLE(xname, reg, lshift, rshift, max, invert) \
+{	.iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, \
+	.info = snd_soc_info_volsw, \
+	.get = snd_soc_dapm_get_volsw, .put = snd_soc_dapm_put_volsw, \
+	.private_value = SOC_DOUBLE_VALUE(reg, lshift, rshift, max, invert, 0) }
 #define SOC_DAPM_SINGLE(xname, reg, shift, max, invert) \
 {	.iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, \
 	.info = snd_soc_info_volsw, \