Extend IntraBC to 4x4

Change-Id: I3f30c35bcd1bc623ad0c34c4b954ff71b2fcfd00
diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index 6d1c69f..fadd930 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -9424,7 +9424,7 @@
                                        RD_STATS *rd_cost, BLOCK_SIZE bsize,
                                        int64_t best_rd) {
   const AV1_COMMON *const cm = &cpi->common;
-  if (bsize < BLOCK_8X8 || !cm->allow_screen_content_tools) return INT64_MAX;
+  if (!av1_allow_intrabc(bsize, cm)) return INT64_MAX;
 
   MACROBLOCKD *const xd = &x->e_mbd;
   const TileInfo *tile = &xd->tile;