riff: add "SM4V" FourCC

Reviewed-by: Ncompn <tempn@twmi.rr.com>
Signed-off-by: NMichael Niedermayer <michaelni@gmx.at>

libavformat/riff.c

@@ -87,6 +87,7 @@ const AVCodecTag ff_codec_bmp_tags[] = {
     { CODEC_ID_MPEG4,        MKTAG('U', 'L', 'D', 'X') },
     { CODEC_ID_MPEG4,        MKTAG('G', 'E', 'O', 'V') },
     { CODEC_ID_MPEG4,        MKTAG('S', 'I', 'P', 'P') }, /* Samsung SHR-6040 */
+    { CODEC_ID_MPEG4,        MKTAG('S', 'M', '4', 'V') },
     { CODEC_ID_MPEG4,        MKTAG('X', 'V', 'I', 'X') },
     { CODEC_ID_MPEG4,        MKTAG('D', 'r', 'e', 'X') },
     { CODEC_ID_MPEG4,        MKTAG('Q', 'M', 'P', '4') }, /* QNAP Systems */