st/va: move H264 enc functions into separate file

Move all H264 encode related functions into separate file. Similar to
VAAPI decode side, there will be separate file for each codec on encode
side as well.

Signed-off-by: Boyuan Zhang <boyuan.zhang@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
5 files changed