ASoC: fsl_sai: evl: enable out-of-band operations

Provide a preparation call for out-of-band requests, which enables
this SAI driver for EVL-controlled I/O.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

sound/soc/fsl/fsl_sai.c

@@ -655,6 +655,12 @@ static void fsl_sai_shutdown(struct snd_pcm_substream *substream,
 			   FSL_SAI_CR3_TRCE_MASK, 0);
 }
 
+static int fsl_sai_prepare_oob(struct snd_pcm_substream *snd_pcm_substream,
+		struct snd_soc_dai *cpu_dai)
+{
+	return 0;
+}
+
 static const struct snd_soc_dai_ops fsl_sai_pcm_dai_ops = {
 	.set_bclk_ratio	= fsl_sai_set_dai_bclk_ratio,
 	.set_sysclk	= fsl_sai_set_dai_sysclk,
@@ -665,6 +671,7 @@ static const struct snd_soc_dai_ops fsl_sai_pcm_dai_ops = {
 	.trigger	= fsl_sai_trigger,
 	.startup	= fsl_sai_startup,
 	.shutdown	= fsl_sai_shutdown,
+	.prepare_oob	= fsl_sai_prepare_oob,
 };
 
 static int fsl_sai_dai_probe(struct snd_soc_dai *cpu_dai)
@@ -890,6 +897,7 @@ static struct regmap_config fsl_sai_regmap_config = {
 	.volatile_reg = fsl_sai_volatile_reg,
 	.writeable_reg = fsl_sai_writeable_reg,
 	.cache_type = REGCACHE_FLAT,
+	.oob_io = IS_ENABLED(CONFIG_EVL),
 };
 
 static int fsl_sai_probe(struct platform_device *pdev)