FPMT: Use cpi->ref_idx_to_skip in get_ref_frames()

The override of is_parallel_encode is removed in
get_ref_frames() so that cpi->ref_idx_to_skip is used
during parallel encode of lower layer frames to
correctly handle the reference frame assignment.

Change-Id: I4dca69d94887e1bfdcd8a4d632cdb6f895438d78
diff --git a/av1/encoder/encode_strategy.c b/av1/encoder/encode_strategy.c
index d1d8283..fe2b9ae 100644
--- a/av1/encoder/encode_strategy.c
+++ b/av1/encoder/encode_strategy.c
@@ -1244,9 +1244,7 @@
         gf_group->frame_parallel_level[gf_index - 1] == 1 &&
         gf_group->update_type[gf_index - 1] == INTNL_ARF_UPDATE) {
       assert(gf_group->update_type[gf_index] == INTNL_ARF_UPDATE);
-      // TODO(Remya): Use original value of is_parallel_encode when FPMT is
-      // enabled.
-      is_parallel_encode = 0;
+
       // If parallel cpis are active, use ref_idx_to_skip, else, use display
       // index.
       assert(IMPLIES(is_parallel_encode, cpi->ref_idx_to_skip != INVALID_IDX));