bitstream: Properly promote av_reverse values before shifting.

libavcodec/bitstream.c

@@ -116,10 +116,10 @@ static int alloc_table(VLC *vlc, int size, int use_static)
 }
 
 static av_always_inline uint32_t bitswap_32(uint32_t x) {
-    return av_reverse[x&0xFF]<<24
+    return (uint32_t)av_reverse[x&0xFF]<<24
-         | av_reverse[(x>>8)&0xFF]<<16
+         | (uint32_t)av_reverse[(x>>8)&0xFF]<<16
-         | av_reverse[(x>>16)&0xFF]<<8
+         | (uint32_t)av_reverse[(x>>16)&0xFF]<<8
-         | av_reverse[x>>24];
+         | (uint32_t)av_reverse[x>>24];
 }
 
 typedef struct {