Simplify plane context fetch

Remove unneeded check condition.

Change-Id: Ie75f8d30a068d91ab24f3ae91197f9cb0466850c
diff --git a/av1/encoder/encodeframe.c b/av1/encoder/encodeframe.c
index 7cdb5c9..0ab2fe1 100644
--- a/av1/encoder/encodeframe.c
+++ b/av1/encoder/encodeframe.c
@@ -2288,8 +2288,7 @@
   const int pl = bsize_at_least_8x8
                      ? partition_plane_context(xd, mi_row, mi_col, bsize)
                      : 0;
-  const int *partition_cost =
-      pl >= 0 ? x->partition_cost[pl] : x->partition_cost[0];
+  const int *partition_cost = x->partition_cost[pl];
 
   int do_rectangular_split = cpi->oxcf.enable_rect_partitions;
   int64_t cur_none_rd = 0;