sdl12-compat: dr_mp3: chop out more sint16 functions.

SDL Commits
1 
From e43bfcc7616435482a2455c003dd29feda6aa3bf Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Mon, 7 Jun 2021 20:47:45 -0400
Subject: [PATCH] dr_mp3: chop out more sint16 functions.

---
 src/dr_mp3.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/dr_mp3.h b/src/dr_mp3.h
index 20f25c2..9e61bdf 100644
--- a/src/dr_mp3.h
+++ b/src/dr_mp3.h
@@ -3551,6 +3551,7 @@ DRMP3_API void drmp3_uninit(drmp3* pMP3)
     drmp3__free_from_callbacks(pMP3->pData, &pMP3->allocationCallbacks);
 }
 
+#ifndef DR_MP3_NO_S16
 #if defined(DR_MP3_FLOAT_OUTPUT)
 static void drmp3_f32_to_s16(drmp3_int16* dst, const float* src, drmp3_uint64 sampleCount)
 {
@@ -3607,6 +3608,7 @@ static void drmp3_s16_to_f32(float* dst, const drmp3_int16* src, drmp3_uint64 sa
     }
 }
 #endif
+#endif
 
 static drmp3_uint64 drmp3_read_pcm_frames_raw(drmp3* pMP3, drmp3_uint64 framesToRead, void* pBufferOut)
 {