SDL_n3dsaudio.h: use triple buffering

(cherry picked from commit 070f57820f401cb962e743bb3a4d12e346d6ed4b)

src/audio/n3ds/SDL_n3dsaudio.h

@@ -24,7 +24,7 @@
 
 #include <3ds.h>
 
-#define NUM_BUFFERS 2 // -- Don't lower this!
+#define NUM_BUFFERS 3 // -- Minimum 2!
 
 struct SDL_PrivateAudioData
 {