audio: minor code readability and formatting fixes

* Fixes 0205059ddb.

audio/audio_hw.c

@@ -86,14 +86,14 @@ struct alsa_stream_out {
 
 static int probe_pcm_out_card() {
     FILE *fp;
-    char card_node[] = "/proc/asound/card0/id";
+    char card_node[32];
     char card_id[16];
 
     char card_prop[PROPERTY_VALUE_MAX];
     property_get("persist.audio.device", card_prop, "");
 
     for (int i = 0; i < 5; i++) {
-        card_node[17] = i + '0';
+        snprintf(card_node, sizeof(card_node), "/proc/asound/card%d/id", i);
         if ((fp = fopen(card_node, "r")) != NULL) {
             fgets(card_id, sizeof(card_id), fp);
             ALOGV("%s: %s", card_node, card_id);