hg: shenandoah/jdk: Fix unsigned comparison in plab.cpp

[ashipile at redhat.com]

Changeset: 0a5a985f076d
Author:    shade
Date:      2018-05-18 14:29 +0200
URL:       http://hg.openjdk.java.net/shenandoah/jdk/rev/0a5a985f076d

Fix unsigned comparison in plab.cpp

! src/hotspot/share/gc/shared/plab.cpp