accessorytest: Remove bad code

This code was calling 'free' on uninitialized stack memory.  However,
we never reached this code due to the while(1) loop, so we weren't
experiencing bad behavior.  Still, we remove this code to avoid
the temptation of copy/paste for someone in the future who might
leave this loop.

Change-Id: I7f4d9528ddc2f92f3118ec1ade630f98bfbacd0c

libs/usb/tests/accessorytest/audio.c

@@ -164,7 +164,6 @@ static void* capture_thread(void* arg)
 static void* play_thread(void* arg)
 {
     struct pcm *pcm = arg;
-    char *buffer;
     int index, err;
 
     fprintf(stderr, "play_thread start\n");
@@ -181,7 +180,6 @@ static void* play_thread(void* arg)
 
     fprintf(stderr, "play_thread done\n");
     pcm_close(pcm);
-    free(buffer);
 
     return NULL;
 }