virgl/video: Add jpeg buf start code check

Add jpeg start code check to fix the issue that
double header adding in virgl video codec.

Signed-off-by: Honglei Huang <honglei1.huang@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: Boyuan Zhang <boyuan.zhang@amd.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Feng Jiang <jiangfeng@kylinos.cn>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22108>

src/gallium/frontends/va/picture.c

@@ -389,6 +389,9 @@ handleVASliceDataBufferType(vlVaContext *context, vlVaBuffer *buf)
          sizes[num_buffers++] = context->mpeg4.start_code_size;
          break;
       case PIPE_VIDEO_FORMAT_JPEG:
+         if (bufHasStartcode(buf, 0xffd8ffdb, 32))
+            break;
+
          vlVaGetJpegSliceHeader(context);
          buffers[num_buffers] = (void *)context->mjpeg.slice_header;
          sizes[num_buffers++] = context->mjpeg.slice_header_size;