AArch64: Fix and enable reverseBytes intrinsic.

There is no revsh on arm64, use rev16 and sxth instead.

Change-Id: I5f9879352f0ad76b386c82cbf476894af888a64c
diff --git a/compiler/dex/quick/gen_invoke.cc b/compiler/dex/quick/gen_invoke.cc
index 55b68e6..b821fb3 100755
--- a/compiler/dex/quick/gen_invoke.cc
+++ b/compiler/dex/quick/gen_invoke.cc
@@ -1385,8 +1385,8 @@
 }
 
 bool Mir2Lir::GenInlinedReverseBytes(CallInfo* info, OpSize size) {
-  if (cu_->instruction_set == kMips || cu_->instruction_set == kArm64) {
-    // TODO - add Mips implementation; Enable Arm64.
+  if (cu_->instruction_set == kMips) {
+    // TODO - add Mips implementation.
     return false;
   }
   RegLocation rl_src_i = info->args[0];