st/va: add encode entrypoint v2

st/va: add encode entrypoint v2

VAAPI passes PIPE_VIDEO_ENTRYPOINT_ENCODE as entry point for encoding case. We
will save this encode entry point in config. config_id was used as profile
previously. Now, config has both profile and entrypoint field, and config_id is
used to get the config object. Later on, we pass this entrypoint to
context->templat.entrypoint instead of always hardcoded to
PIPE_VIDEO_ENTRYPOINT_BITSTREAM for decoding case previously. Encode entrypoint
is not accepted by driver until we enable Vaapi encode in later patch.

v2 (chk): fix commit message to match 80 chars, use switch instead of ifs,
	  fix memory leaks in the error path, implement vlVaQueryConfigEntrypoints
	  as well, drop VAEntrypointEncPicture (only used for JPEG).

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