lavc/vaapi_h264: Do not set FMO fields.

The fields are deprecated in current vaapi,
setting them to 0 in old versions is fine
as FMO is not implemented.

Fixes the following warnings:
libavcodec/vaapi_h264.c:259:10: warning: 'num_slice_groups_minus1' is deprecated [-Wdeprecated-declarations]
        .num_slice_groups_minus1                    = pps->slice_group_count - 1,
         ^
libavcodec/vaapi_h264.c:260:10: warning: 'slice_group_map_type' is deprecated [-Wdeprecated-declarations]
        .slice_group_map_type                       = pps->mb_slice_group_map_type,
         ^
libavcodec/vaapi_h264.c:261:10: warning: 'slice_group_change_rate_minus1' is deprecated [-Wdeprecated-declarations]
        .slice_group_change_rate_minus1             = 0, /* FMO is not implemented */
         ^

Reviewed-by: Mark Thompson

libavcodec/vaapi_h264.c

@@ -256,9 +256,6 @@ static int vaapi_h264_start_frame(AVCodecContext          *avctx,
             .log2_max_pic_order_cnt_lsb_minus4      = sps->log2_max_poc_lsb - 4,
             .delta_pic_order_always_zero_flag       = sps->delta_pic_order_always_zero_flag,
         },
-        .num_slice_groups_minus1                    = pps->slice_group_count - 1,
-        .slice_group_map_type                       = pps->mb_slice_group_map_type,
-        .slice_group_change_rate_minus1             = 0, /* FMO is not implemented */
         .pic_init_qp_minus26                        = pps->init_qp - 26,
         .pic_init_qs_minus26                        = pps->init_qs - 26,
         .chroma_qp_index_offset                     = pps->chroma_qp_index_offset[0],