ASoC: Intel: check and clear runtime module pointer

Add check runtime module pointers before freeing them, and clear
them to NULL after freed.

With this implemented, we can avoid NULL pointer dereference or
double free errors.
Signed-off-by: NJie Yang <yang.jie@intel.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

sound/soc/intel/haswell/sst-haswell-pcm.c

@@ -928,10 +928,15 @@ static void hsw_pcm_free_modules(struct hsw_priv_data *pdata)
 
 	for (i = 0; i < ARRAY_SIZE(mod_map); i++) {
 		pcm_data = &pdata->pcm[mod_map[i].dai_id][mod_map[i].stream];
-		sst_hsw_runtime_module_free(pcm_data->runtime);
+		if (pcm_data->runtime){
+			sst_hsw_runtime_module_free(pcm_data->runtime);
+			pcm_data->runtime = NULL;
+		}
 	}
-	if (sst_hsw_is_module_loaded(hsw, SST_HSW_MODULE_WAVES)) {
+	if (sst_hsw_is_module_loaded(hsw, SST_HSW_MODULE_WAVES) &&
+				pdata->runtime_waves) {
 		sst_hsw_runtime_module_free(pdata->runtime_waves);
+		pdata->runtime_waves = NULL;
 	}
 }