Align encoder stats update on delta_qindex and delta_lflevel

This patch is to add the according changes to update_stats() on the
encoder side for signaling of delta_qindex and delta_lflevel, aligned
with the following CL:
https://aomedia-review.googlesource.com/c/aom/+/30801

BUG=aomedia:992

Change-Id: Ie627d4ebce085da85bcee7d5d3f9a7c358725481
diff --git a/av1/encoder/encodeframe.c b/av1/encoder/encodeframe.c
index ae061e5..99d0d6d 100644
--- a/av1/encoder/encodeframe.c
+++ b/av1/encoder/encodeframe.c
@@ -934,8 +934,8 @@
   const uint8_t allow_update_cdf = tile_data->allow_update_cdf;
 
   // delta quant applies to both intra and inter
-  int super_block_upper_left =
-      ((mi_row & MAX_MIB_MASK) == 0) && ((mi_col & MAX_MIB_MASK) == 0);
+  const int super_block_upper_left = ((mi_row & (cm->mib_size - 1)) == 0) &&
+                                     ((mi_col & (cm->mib_size - 1)) == 0);
 
   const int seg_ref_active =
       segfeature_active(&cm->seg, mbmi->segment_id, SEG_LVL_REF_FRAME);