cmd/compile: do not fold large offset on ARM64

Fixes #18933.

Change-Id: I8bb98e95bb4486a086d93bcf99e3a37488e77b03
Reviewed-on: https://go-review.googlesource.com/36318
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

test/fixedbugs/issue6036.go

-// +build amd64
+// +build !386,!arm,!mips,!mipsle,!amd64p32
 // compile
 
 // Copyright 2013 The Go Authors. All rights reserved.