lavc/vaapi_encode: add EQUAL_MULTI_ROWS support for slice structure
VA_ENC_SLICE_STRUCTURE_EQUAL_MULTI_ROWS is added to in the latest
libva (1.8.0) which matches the hardware behaviour:
/** \brief Driver supports any number of rows per slice but they must
* be the same for all slices except for the last one, which must be
* equal or smaller to the previous slices.
*/
And VA_ENC_SLICE_STRUCTURE_EQUAL_ROWS is kind of deprecated for iHD
since it's somehow introduced in [1] which is misleading from what we
actually handles.
[1]<https://github.com/intel/libva/commit/
0e6d5441f19bdc674b4da3169d614d10fd644778>
Signed-off-by: Linjie Fu <linjie.justin.fu@gmail.com>