avformat/utils: Check negative bps before shifting in ff_get_pcm_codec_id()

Fixes: undefined shift.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/utils.c

@@ -2955,7 +2955,7 @@ enum AVCodecID ff_codec_get_id(const AVCodecTag *tags, unsigned int tag)
 
 enum AVCodecID ff_get_pcm_codec_id(int bps, int flt, int be, int sflags)
 {
-    if (bps > 64U)
+    if (bps <= 0 || bps > 64)
         return AV_CODEC_ID_NONE;
 
     if (flt) {