Prune one-sided compound at speed 0

This patch extends the pruning of one-sided compound reference frames
when not all the reference frames are one-sided to speed 0.

The logic is enabled via the speed feature `selective_ref_frame=1`.

Encoder performance results averaged over all resolutions are as
follows:

      Instruction Count               BD-Rate Loss(%)
cpu     Reduction(%)     avg.psnr  ovr.psnr   ssim    vmaf   vmaf_neg
 0        15.721          0.1080    0.1134   0.0761  0.0467   0.0452

STATS_CHANGED for speed = 0

Change-Id: I89955869fd5cdf8b097c5a1f161fed7f04f0f155

av1/encoder/encodeframe.c

diff --git a/av1/encoder/encodeframe.c b/av1/encoder/encodeframe.c
index 1ccff9e..9d2292c 100644
--- a/av1/encoder/encodeframe.c
+++ b/av1/encoder/encodeframe.c
@@ -1807,7 +1807,7 @@
     // Disable all compound references
     cpi->prune_ref_frame_mask = (1 << MODE_CTX_REF_FRAMES) - (1 << REF_FRAMES);
   } else if (!cpi->sf.rt_sf.use_nonrd_pick_mode &&
-             cpi->sf.inter_sf.selective_ref_frame >= 2) {
+             cpi->sf.inter_sf.selective_ref_frame >= 1) {
     AV1_COMMON *const cm = &cpi->common;
     const int cur_frame_display_order_hint =
         cm->current_frame.display_order_hint;