ARM: enable optimisation for easy multiply, add modulus pattern.

Fix the issue when src/dest registers overlap in easy multiply.

Change-Id: Ie8cc098c29c74fd06c1b67359ef94f2c6b88a71e
diff --git a/compiler/dex/quick/gen_common.cc b/compiler/dex/quick/gen_common.cc
index 7af9d57..2a27018 100644
--- a/compiler/dex/quick/gen_common.cc
+++ b/compiler/dex/quick/gen_common.cc
@@ -1650,9 +1650,8 @@
     StoreValue(rl_dest, rl_result);
     return true;
   }
-  // There is RegRegRegShift on Arm, so check for more special cases.
-  // TODO: disabled, need to handle case of "dest == src" properly.
-  if (false && cu_->instruction_set == kThumb2) {
+  // There is RegRegRegShift on Arm, so check for more special cases
+  if (cu_->instruction_set == kThumb2) {
     return EasyMultiply(rl_src, rl_dest, lit);
   }
   // Can we simplify this multiplication?