libavformat/mpegts.c: fix hardcoded 5-bytes skip for metadata streams.

Before the introduction of AV_CODEC_ID_TIMED_ID3 for timed_id3 metadata streams
in mpegts (commit 4a4437c), AV_CODEC_ID_SMPTE_KLV
was the only existing codec for metadata.

It seems that this codec has a 5-bytes metadata header[1] that, for some reason,
was always skipped when decoding data packets.

However, when working with a AV_CODEC_ID_TIMED_ID3 streams, this results in the
5 first bytes of the payload being cut-off, which includes essential informations
such as the ID3 tag version.

This patch fixes the issue by keeping the 5-bytes skip only for AV_CODEC_ID_SMPTE_KLV
streams.

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/mpegts.c

@@ -1305,7 +1305,7 @@ static int mpegts_push_data(MpegTSFilter *filter,
                     p += sl_header_bytes;
                     buf_size -= sl_header_bytes;
                 }
-                if (pes->stream_type == 0x15 && buf_size >= 5) {
+                if (pes->st->codecpar->codec_id == AV_CODEC_ID_SMPTE_KLV && buf_size >= 5) {
                     /* skip metadata access unit header */
                     pes->pes_header_size += 5;
                     p += 5;