va: vpp: Add raw buffer copy when needed.
Just like the decoder, the vapostproc also needs to copy the output buffer to raw buffer if downstream elements only supports raw caps and does not support the video meta.
The pipeline like:
gst-launch-1.0 filesrc location=xxxx ! h264parse ! vah264dec !
vapostproc ! capsfilter caps=video/x-raw,width=55,height=128 !
filesink location=xxx
needs this logic to dump the data correctly.