[ARM simulator] Fix vrev for Neon64-Neon16.

Bug: v8:750454
Change-Id: Ia270d2ede546bdc0b8a61b944dada59905a5c862
Reviewed-on: https://chromium-review.googlesource.com/594490Reviewed-by: Martyn Capewell <martyn.capewell@arm.com>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47045}

src/arm/simulator-arm.cc

@@ -5220,7 +5220,7 @@ void Simulator::DecodeSpecialCondition(Instruction* instr) {
                 case Neon16: {
                   uint16_t src[8];
                   get_neon_register(Vm, src);
-                  for (int i = 0; i < 4; i++) {
+                  for (int i = 0; i < 2; i++) {
                     std::swap(src[i * 4], src[i * 4 + 3]);
                     std::swap(src[i * 4 + 1], src[i * 4 + 2]);
                   }