MIPS64: Fix `[callbacks] Properly support RCS for ApiAccessors and Callbacks.`

Fix 0027c834

FLAG_runtime_stats was declared as Int but it was accessed as
pointer. On 64-bit architectures pointer access needs to be
eight byte aligned. This created unaligned memory access
on 64-bit architectures for those architectures that do not
support unaligned memory access.

TEST=mjsunit/wasm/table,cctest/test-accessors/AccessorIC

Change-Id: I569b69583de98b4c5fb7266f23f927bbd006966d
Reviewed-on: https://chromium-review.googlesource.com/1177601
Commit-Queue: Ivica Bogosavljevic <ibogosavljevic@wavecomp.com>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55166}

src/code-stub-assembler.cc

@@ -12085,10 +12085,10 @@ Node* CodeStubAssembler::IsDebugActive() {
 }
 
 TNode<BoolT> CodeStubAssembler::IsRuntimeCallStatsEnabled() {
-  TNode<UintPtrT> flag_value = UncheckedCast<UintPtrT>(Load(
-      MachineType::IntPtr(),
+  TNode<Word32T> flag_value = UncheckedCast<Word32T>(Load(
+      MachineType::Int32(),
       ExternalConstant(ExternalReference::address_of_runtime_stats_flag())));
-  return WordNotEqual(flag_value, IntPtrConstant(0));
+  return Word32NotEqual(flag_value, Int32Constant(0));
 }
 
 Node* CodeStubAssembler::IsPromiseHookEnabled() {