Add TRACKS_ALL, remove BGCntrlBitfield

src/battle_controller_link_opponent.c

@@ -323,7 +323,7 @@ static void Intro_TryShinyAnimShowHealthbox(void)
             }
             else
             {
-                m4aMPlayVolumeControl(&gMPlayInfo_BGM, 0xFFFF, 0x100);
+                m4aMPlayVolumeControl(&gMPlayInfo_BGM, TRACKS_ALL, 0x100);
             }
         }
 
@@ -465,7 +465,7 @@ static void SwitchIn_HandleSoundAndEnd(void)
         if (gSprites[gBattlerSpriteIds[gActiveBattler]].callback == SpriteCallbackDummy
             || gSprites[gBattlerSpriteIds[gActiveBattler]].callback == SpriteCallbackDummy_2)
         {
-            m4aMPlayVolumeControl(&gMPlayInfo_BGM, 0xFFFF, 0x100);
+            m4aMPlayVolumeControl(&gMPlayInfo_BGM, TRACKS_ALL, 0x100);
             LinkOpponentBufferExecCompleted();
         }
     }