Encoding: Update the comment for the data structure about the packed rawdata/slice_header data
Encoding: Update the comment for the data structure about the packed rawdata/slice_header data

Signed-off-by: Zhao Yakui <21bae65ecea50a19bd9d0fef489914760189fd5b@intel.com>
(cherry picked from commit 56715c893fa87e2d3af2938b9202d75cdc79a8fd)

chenxianqin/vaapi-intel-driver,gbeauchesne/libva-intel-driver,01org/iotg-lin-gfx-va-driver,uartie/vaapi-intel-driver,gbeauchesne/libva-intel-driver,uartie/vaapi-intel-driver,01org/iotg-lin-gfx-va-driver,01org/iotg-lin-gfx-va-driver,chenxianqin/vaapi-intel-driver,chenxianqin/vaapi-intel-driver,01org/iotg-lin-gfx-va-driver,gbeauchesne/libva-intel-driver,chenxianqin/vaapi-intel-driver,chenxianqin/vaapi-intel-driver,uartie/vaapi-intel-driver,gbeauchesne/libva-intel-driver,uartie/vaapi-intel-driver,01org/iotg-lin-gfx-va-driver,uartie/vaapi-intel-driver,gbeauchesne/libva-intel-driver