Instead issue a memory barrier on ARMv7 after reading the address.

Fixes #23777

Change-Id: I7aff2ab0246af64b437ebe0b31d4b30d351890d8
Reviewed-on: https://go-review.googlesource.com/94275Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>