vpxdec: fix use of uninitialized memory for raw files

The sz member of the vpx_codec_stream_info_t structure must be
initialized when passed to vpx_codec_peek_stream_info().

Change-Id: I2d13d287d9639262b932cf44671a595fdf3c38ef

vpxdec.c

@@ -442,6 +442,8 @@ unsigned int file_is_raw(FILE *infile,
     int is_raw = 0;
     vpx_codec_stream_info_t si;
 
+    si.sz = sizeof(si);
+
     if (fread(buf, 1, 32, infile) == 32)
     {
         int i;