Eliminate suspend checks on back-edges to return insn.

This optimization seems to have been broken for a long time.

Change-Id: I62ec85c71bb5253917ad9465a952911e917f6b52
diff --git a/compiler/dex/mir_graph.h b/compiler/dex/mir_graph.h
index 63b1f2d..c8ea972 100644
--- a/compiler/dex/mir_graph.h
+++ b/compiler/dex/mir_graph.h
@@ -444,6 +444,11 @@
   void UpdatePredecessor(BasicBlockId old_pred, BasicBlockId new_pred);
 
   /**
+   * @brief Return first non-Phi insn.
+   */
+  MIR* GetFirstNonPhiInsn();
+
+  /**
    * @brief Used to obtain the next MIR that follows unconditionally.
    * @details The implementation does not guarantee that a MIR does not
    * follow even if this method returns nullptr.