[Normative] Correctly get filter level for u, v plane

This part of code is in effect only when deltaq-mode = 2.

BUG=aomedia:1653

Change-Id: Id10c1fd0885f2313c44dca0adb96d49f61f516cb

av1/common/av1_loopfilter.c

diff --git a/av1/common/av1_loopfilter.c b/av1/common/av1_loopfilter.c
index a9f489e..a871148 100644
--- a/av1/common/av1_loopfilter.c
+++ b/av1/common/av1_loopfilter.c
@@ -555,8 +555,14 @@
     } else {
       delta_lf = mbmi->current_delta_lf_from_base;
     }
-    int lvl_seg =
-        clamp(delta_lf + cm->lf.filter_level[dir_idx], 0, MAX_LOOP_FILTER);
+    int base_level;
+    if (plane == 0)
+      base_level = cm->lf.filter_level[dir_idx];
+    else if (plane == 1)
+      base_level = cm->lf.filter_level_u;
+    else
+      base_level = cm->lf.filter_level_v;
+    int lvl_seg = clamp(delta_lf + base_level, 0, MAX_LOOP_FILTER);
     assert(plane >= 0 && plane <= 2);
     const int seg_lf_feature_id = seg_lvl_lf_lut[plane][dir_idx];
     if (segfeature_active(&cm->seg, segment_id, seg_lf_feature_id)) {