ASoC: Allow unspecified source when stopping WM8994 FLLs

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/wm8994.c

@@ -2853,6 +2853,11 @@ static int wm8994_set_fll(struct snd_soc_dai *dai, int id, int src,
 	}
 
 	switch (src) {
+	case 0:
+		/* Allow no source specification when stopping */
+		if (freq_out)
+			return -EINVAL;
+		break;
 	case WM8994_FLL_SRC_MCLK1:
 	case WM8994_FLL_SRC_MCLK2:
 	case WM8994_FLL_SRC_LRCLK: