decoder/mad: simplify "return", eliminate check

This check was redundant, because we could only exit the loop when
ret==DECODE_OK.

src/decoder/plugins/MadDecoderPlugin.cxx

@@ -1043,10 +1043,8 @@ MadDecoder::Read()
 		}
 
 		if (!skip && ret == DECODE_OK)
-			break;
+			return true;
 	}
-
-	return ret != DECODE_BREAK;
 }
 
 static void