Fix inter predictor route condition

Fix a bug introduced in the previous commit that effectively
disables chroma-sub8x8.

Change-Id: I521fdc1f15f5bed5272081217e70d1e2549c7ecd

av1/common/reconinter.c

diff --git a/av1/common/reconinter.c b/av1/common/reconinter.c
index a797bf5..9de8e34 100644
--- a/av1/common/reconinter.c
+++ b/av1/common/reconinter.c
@@ -933,7 +933,7 @@
 
 #if CONFIG_CHROMA_SUB8X8
   const BLOCK_SIZE bsize = mi->mbmi.sb_type;
-  int sub8x8_inter = (bw < 4) || (bh < 4);
+  int sub8x8_inter = bsize < BLOCK_8X8 && plane;
   const int row_start = (block_size_high[bsize] == 4) ? -1 : 0;
   const int col_start = (block_size_wide[bsize] == 4) ? -1 : 0;