Keep track of reference picture buffer reallocation (fixes: #5868)

The reference buffer address is used as the indication in h264 DPB Tier2, when reference buffer was reallocated, h264 DPB would lose track of that reference picture. Adding a pointer obsolete_buf in vlVaSurface data structure for tracking this released buffer, also in h264_picture_desc adding a private field, which contains past_ref[16] for tracking previously released buffer vs current buffer for reference frames.

In order to keep track of reference frame buffer address changing, using past_ref to compare with render_pic_list, once the one in past_ref is valid and if render_pic_list has that entry, it will need to update it to the latest one in ref[i].

Signed-off-by: Ruijing Dong ruijing.dong@amd.com