Revert "Null check elimination improvement"

This reverts commit 4db179d1821a9e78819d5adc8057a72f49e2aed8.

Change-Id: I059c15c85860c6c9f235b5dabaaef2edebaf1de2
diff --git a/compiler/dex/mir_dataflow.cc b/compiler/dex/mir_dataflow.cc
index 11e19dc..9c8ce23 100644
--- a/compiler/dex/mir_dataflow.cc
+++ b/compiler/dex/mir_dataflow.cc
@@ -1243,8 +1243,7 @@
     if (mir->ssa_rep == NULL) {
       continue;
     }
-    // Each level of nesting adds *16 to count, up to 3 levels deep.
-    uint32_t weight = std::min(3U, static_cast<uint32_t>(bb->nesting_depth) * 4);
+    uint32_t weight = std::min(16U, static_cast<uint32_t>(bb->nesting_depth));
     for (int i = 0; i < mir->ssa_rep->num_uses; i++) {
       int s_reg = mir->ssa_rep->uses[i];
       raw_use_counts_.Increment(s_reg);