ASoC: fsl_sai: Enable MCTL_MCLK_EN bit for master mode

On i.MX8MM, the MCTL_MCLK_EN bit it is not only the gate
for MCLK output to PAD, but also the gate bit between
root clock and SAI module, So it is need to be enabled
for master mode, otherwise there is no bclk generated.
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Link: https://lore.kernel.org/r/1652963808-14515-1-git-send-email-shengjiu.wang@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/fsl/fsl_sai.c

@@ -437,6 +437,12 @@ static int fsl_sai_set_bclk(struct snd_soc_dai *dai, bool tx, u32 freq)
 				   FSL_SAI_CR2_DIV_MASK | FSL_SAI_CR2_BYP,
 				   savediv / 2 - 1);
 
+	if (sai->soc_data->max_register >= FSL_SAI_MCTL) {
+		/* SAI is in master mode at this point, so enable MCLK */
+		regmap_update_bits(sai->regmap, FSL_SAI_MCTL,
+				   FSL_SAI_MCTL_MCLK_EN, FSL_SAI_MCTL_MCLK_EN);
+	}
+
 	return 0;
 }