speaker-test: Add missing draining at the end

Without the call of snd_pcm_drain() the pending data on the buffer
might be discarded, which results in the abort of playback sound in
the middle.  Let's fix it.

Reported-and-tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

speaker-test/speaker-test.c

@@ -1307,6 +1307,7 @@ int main(int argc, char *argv[]) {
     }
   }
 
+  snd_pcm_drain(handle);
 
   free(frames);
 #ifdef CONFIG_SUPPORT_CHMAP