hg: jdk9/hs-comp/hotspot: 8139042: AARCH64: Correct regression introduced by 8080293

[adinn at redhat.com]

Changeset: 30f10e51ad6f
Author:    adinn
Date:      2015-10-07 06:56 -0400
URL:       http://hg.openjdk.java.net/jdk9/hs-comp/hotspot/rev/30f10e51ad6f

8139042: AARCH64: Correct regression introduced by 8080293
Summary: Reinstate unsafe volatile optimization broken by JDK-8080293
Reviewed-by: aph, kvn

! src/cpu/aarch64/vm/aarch64.ad