mp3enc: remove unneeded ifdef

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mp3enc.c

@@ -412,9 +412,7 @@ static int mp3_write_packet(AVFormatContext *s, AVPacket *pkt)
     else {
         MP3Context  *mp3 = s->priv_data;
         MPADecodeHeader c;
-#ifdef FILTER_VBR_HEADERS
         int base;
-#endif
 
         ff_mpegaudio_decode_header(&c, AV_RB32(pkt->data));