ASoC: rt1316: fix key tone missing

This patch adds a control that there are three options to control the digital volume output.
The user could select "immediately" to make volume updates immediately
and avoid key tone missing issues.
In default, the driver selects that the volume update when a zero-crossing with a soft ramp.

Signed-off-by: Shuming Fan <[e-mail]>
Reported-by: Vijendar Mukunda <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

sound/soc/codecs/rt1316-sdw.c

···
 	SDW_SDCA_CTL(FUNC_NUM_SMART_AMP, RT1316_SDCA_ENT_UDMPU21, RT1316_SDCA_CTL_UDMPU_CLUSTER, 0), 0,
 	rt1316_rx_data_ch_select);
 
+static const char * const rt1316_dac_output_vol_select[] = {
+	"immediately",
+	"zero crossing",
+	"zero crossing with soft ramp",
+};
+
+static SOC_ENUM_SINGLE_DECL(rt1316_dac_vol_ctl_enum,
+	0xc010, 6, rt1316_dac_output_vol_select);
+
 static const struct snd_kcontrol_new rt1316_snd_controls[] = {
 
 	/* I2S Data Channel Selection */
···
 	/* IV mixer Control */
 	SOC_DOUBLE("Isense Mixer Switch", 0xc605, 2, 0, 1, 1),
 	SOC_DOUBLE("Vsense Mixer Switch", 0xc605, 3, 1, 1, 1),
+
+	/* DAC Output Volume Control */
+	SOC_ENUM("DAC Output Vol Control", rt1316_dac_vol_ctl_enum),
 };
 
 static const struct snd_kcontrol_new rt1316_sto_dac =