ASoC: rsnd: DVC kctrl sets once

Same DVC might be used few times if system/platform is using MIX.
For example below case.

	DAI0 playback = <&src0 &ctu02 &mix0 &dvc0 &ssi0>;
	DAI1 playback = <&src2 &ctu03 &mix0 &dvc0 &ssi0>;

This case, ALSA will have DVC,0 and DVC,1 kcontrol interfaces,
but these are same DVC. This is confusing.
This patch adds new flags and avoid such case.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Tested-by: Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sh/rcar/dvc.c

@@ -44,8 +44,11 @@ struct rsnd_dvc {
 	struct rsnd_kctrl_cfg_s ren;	/* Ramp Enable */
 	struct rsnd_kctrl_cfg_s rup;	/* Ramp Rate Up */
 	struct rsnd_kctrl_cfg_s rdown;	/* Ramp Rate Down */
+	u32 flags;
 };
 
+#define KCTRL_INITIALIZED	(1 << 0)
+
 #define rsnd_dvc_get(priv, id) ((struct rsnd_dvc *)(priv->dvc) + id)
 #define rsnd_dvc_nr(priv) ((priv)->dvc_nr)
 
@@ -254,6 +257,9 @@ static int rsnd_dvc_pcm_new(struct rsnd_mod *mod,
 	int channels = rsnd_rdai_channels_get(rdai);
 	int ret;
 
+	if (rsnd_flags_has(dvc, KCTRL_INITIALIZED))
+		return 0;
+
 	/* Volume */
 	ret = rsnd_kctrl_new_m(mod, io, rtd,
 			is_play ?
@@ -307,6 +313,8 @@ static int rsnd_dvc_pcm_new(struct rsnd_mod *mod,
 	if (ret < 0)
 		return ret;
 
+	rsnd_flags_set(dvc, KCTRL_INITIALIZED);
+
 	return 0;
 }