Consolidate get_scaled_plane_bsize()

get_scaled_plane_bsize() and get_plane_block_size() are essentially the
same and can thus be merged.

Change-Id: Ia4fb7c87b5df07de9b6b22cd6cc83fbf4967af50
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 44b9143..03d492e 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -1392,7 +1392,7 @@
   assert(bsize < BLOCK_SIZES_ALL);
   const int ss_x = pd->subsampling_x;
   const int ss_y = pd->subsampling_y;
-  const BLOCK_SIZE plane_bsize = get_scaled_plane_bsize(bsize, ss_x, ss_y);
+  const BLOCK_SIZE plane_bsize = get_plane_block_size(bsize, ss_x, ss_y);
   assert(plane_bsize < BLOCK_SIZES_ALL);
   const TX_SIZE max_tx_size = get_vartx_max_txsize(xd, plane_bsize, plane);
   const int step =