passing audio test 4

include/audio.h

@@ -20,6 +20,9 @@ typedef struct {
     bool ch4_dac;
 
     bool ch1_len_fz;
+    bool ch2_len_fz;
+    bool ch3_len_fz;
+    bool ch4_len_fz;
 
     u8 volume_left;
     u8 volume_right;