Remove the link from dalvik instruction back to kMirOpCheck.

Free the MIR::meta for another use on PUT/GET instructions.

Change-Id: Ic5a5cc5026e2076031d7b8ce7f2b36c185bfc93a
diff --git a/compiler/dex/mir_graph.h b/compiler/dex/mir_graph.h
index bbcea10..4666d1e 100644
--- a/compiler/dex/mir_graph.h
+++ b/compiler/dex/mir_graph.h
@@ -253,7 +253,7 @@
   union {
     // Incoming edges for phi node.
     BasicBlockId* phi_incoming;
-    // Establish link between two halves of throwing instructions.
+    // Establish link from check instruction (kMirOpCheck) to the actual throwing instruction.
     MIR* throw_insn;
     // Fused cmp branch condition.
     ConditionCode ccode;