ASoC: don't dereference NULL pcm_{new,free}

Not all platform drivers have pcm_{new,free} callbacks. Seen with a
"snd-soc-dummy" codec from sound/soc/rockchip/rk3399_gru_sound.c.

Fixes: 99b04f4c ("ASoC: add Component level pcm_new/pcm_free")
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-core.c

@@ -3326,7 +3326,10 @@ static int snd_soc_platform_drv_pcm_new(struct snd_soc_pcm_runtime *rtd)
 {
 	struct snd_soc_platform *platform = rtd->platform;
 
-	return platform->driver->pcm_new(rtd);
+	if (platform->driver->pcm_new)
+		return platform->driver->pcm_new(rtd);
+	else
+		return 0;
 }
 
 static void snd_soc_platform_drv_pcm_free(struct snd_pcm *pcm)
@@ -3334,7 +3337,8 @@ static void snd_soc_platform_drv_pcm_free(struct snd_pcm *pcm)
 	struct snd_soc_pcm_runtime *rtd = pcm->private_data;
 	struct snd_soc_platform *platform = rtd->platform;
 
-	platform->driver->pcm_free(pcm);
+	if (platform->driver->pcm_free)
+		platform->driver->pcm_free(pcm);
 }
 
 /**