mvp: fall back to 16 bit audio samples

Looks like the MVP audio output only supports 16 and 24 bit audio
samples.  If MPD generates any other sample formats, force it to use
16 bit.

NEWS

@@ -18,6 +18,7 @@ ver 0.15 - (200?/??/??)
   - shout: enlarged buffer size to 32 kB
   - null: allow disabling synchronization
   - mvp: fall back to stereo
+  - mvp: fall back to 16 bit audio samples
 * commands:
   - "playlistinfo" supports a range now
   - added "sticker database", command "sticker", which allows clients

src/output/mvp_plugin.c

@@ -152,7 +152,11 @@ mvp_set_pcm_params(struct mvp_data *md, struct audio_format *audio_format)
 		break;
 
 	default:
-		return false;
+		g_debug("unsupported sample format %u - falling back to stereo",
+			audio_format->bits);
+		audio_format->bits = 16;
+		mix[1] = 2;
+		break;
 	}
 
 	mix[3] = 0;	/* stream type? */