vaapi_encode: Use gop_size consistently in RC parameters

The non-H.26[45] codecs already use this form.  Since we don't
currently generate I frames for codecs which support them separately
to IDR, the p_per_i variable is set to infinity by default so that it
doesn't interfere with any other calculation.  (All the code for I
frames still exists, and it works for H.264 if set manually.)

(cherry picked from commit 6af014f402)

libavcodec/vaapi_encode.c

@@ -1435,8 +1435,7 @@ av_cold int ff_vaapi_encode_init(AVCodecContext *avctx)
     ctx->output_order = - ctx->output_delay - 1;
 
     // Currently we never generate I frames, only IDR.
-    ctx->p_per_i = ((avctx->gop_size - 1 + avctx->max_b_frames) /
-                    (avctx->max_b_frames + 1));
+    ctx->p_per_i = INT_MAX;
     ctx->b_per_p = avctx->max_b_frames;
 
     if (ctx->codec->sequence_params_size > 0) {

libavcodec/vaapi_encode_h264.c

@@ -905,8 +905,8 @@ static int vaapi_encode_h264_init_sequence_params(AVCodecContext *avctx)
             mseq->nal_hrd_parameters_present_flag = 0;
         }
 
-        vseq->intra_period     = ctx->p_per_i * (ctx->b_per_p + 1);
-        vseq->intra_idr_period = vseq->intra_period;
+        vseq->intra_period     = avctx->gop_size;
+        vseq->intra_idr_period = avctx->gop_size;
         vseq->ip_period        = ctx->b_per_p + 1;
     }
 

libavcodec/vaapi_encode_h265.c

@@ -832,8 +832,8 @@ static int vaapi_encode_h265_init_sequence_params(AVCodecContext *avctx)
             vseq->vui_time_scale        = avctx->time_base.den;
         }
 
-        vseq->intra_period     = ctx->p_per_i * (ctx->b_per_p + 1);
-        vseq->intra_idr_period = vseq->intra_period;
+        vseq->intra_period     = avctx->gop_size;
+        vseq->intra_idr_period = avctx->gop_size;
         vseq->ip_period        = ctx->b_per_p + 1;
     }