ASoC: tas2770: Add missing bias level power states

Add the BIAS_STANDBY and BIAS_PREPARE to the set_bias_level or else the
driver will return -EINVAL which is not correct as they are valid
states.

Fixes: 1a476abc ("tas2770: add tas2770 smart PA kernel driver")
Signed-off-by: NDan Murphy <dmurphy@ti.com>
Link: https://lore.kernel.org/r/20200918190548.12598-2-dmurphy@ti.comSigned-off-by: NMark Brown <broonie@kernel.org>

sound/soc/codecs/tas2770.c

@@ -57,7 +57,12 @@ static int tas2770_set_bias_level(struct snd_soc_component *component,
 			TAS2770_PWR_CTRL_MASK,
 			TAS2770_PWR_CTRL_ACTIVE);
 		break;
-
+	case SND_SOC_BIAS_STANDBY:
+	case SND_SOC_BIAS_PREPARE:
+		snd_soc_component_update_bits(component,
+			TAS2770_PWR_CTRL,
+			TAS2770_PWR_CTRL_MASK, TAS2770_PWR_CTRL_MUTE);
+		break;
 	case SND_SOC_BIAS_OFF:
 		snd_soc_component_update_bits(component,
 			TAS2770_PWR_CTRL,