ASoC: Provide default set_bias_level() implementation

If the CODEC does not provide a set_bias_level() then update the
bias_level variable for it since other parts of the system expect
that to be maintained.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/soc-dapm.c

@@ -148,8 +148,12 @@ static int snd_soc_dapm_set_bias_level(struct snd_soc_device *socdev,
 
 	if (card->set_bias_level)
 		ret = card->set_bias_level(card, level);
-	if (ret == 0 && codec->set_bias_level)
+	if (ret == 0) {
+		if (codec->set_bias_level)
 			ret = codec->set_bias_level(codec, level);
+		else
+			codec->bias_level = level;
+	}
 
 	return ret;
 }