[arm64] Enable write-protected code pages.

R=ulan@chromium.org
BUG=chromium:845877

Change-Id: If8a9e2f107bb775494b1d4a83c3fb045bb846b10
Reviewed-on: https://chromium-review.googlesource.com/c/1347482Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57740}

src/flag-definitions.h

@@ -699,7 +699,7 @@ DEFINE_BOOL(incremental_marking_wrappers, true,
 DEFINE_BOOL(trace_unmapper, false, "Trace the unmapping")
 DEFINE_BOOL(parallel_scavenge, true, "parallel scavenge")
 DEFINE_BOOL(trace_parallel_scavenge, false, "trace parallel scavenge")
-#if defined(V8_TARGET_ARCH_ARM) || defined(V8_TARGET_ARCH_ARM64)
+#if defined(V8_TARGET_ARCH_ARM)
 #define V8_WRITE_PROTECT_CODE_MEMORY_BOOL false
 #else
 #define V8_WRITE_PROTECT_CODE_MEMORY_BOOL true