SDL: testsurround: fix order of arguments of callback

SDL Commits
1 
From 1b03a2430a7e4735ba37f1b55e9eb64c136d1641 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Mon, 28 Aug 2023 00:12:59 +0200
Subject: [PATCH] testsurround: fix order of arguments of callback

---
 test/testsurround.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/testsurround.c b/test/testsurround.c
index 4bd51a907a95..53dc58dacfba 100644
--- a/test/testsurround.c
+++ b/test/testsurround.c
@@ -96,7 +96,7 @@ static SDL_bool is_lfe_channel(int channel_index, int channel_count)
     return (channel_count == 3 && channel_index == 2) || (channel_count >= 6 && channel_index == 3);
 }
 
-static void SDLCALL fill_buffer(SDL_AudioStream *stream, int len, void *unused)
+static void SDLCALL fill_buffer(void *userdata, SDL_AudioStream *stream, int len)
 {
     const int samples = len / sizeof(Sint16);
     Sint16 *buffer = NULL;