RFR(11): Add missing include after latest CAS streamlining

[Roman Kennke]

-PCH exposes a problem with missing include in sh/jdk11. The include is
present in jdk/jdk.

Testing: build with -PCH

Ok?

diff -r 674ff4da0611
src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.cpp
--- a/src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.cpp	Thu
May 30 12:53:32 2019 +0200
+++ b/src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.cpp	Tue
Jun 04 11:29:52 2019 +0200
@@ -32,6 +32,7 @@
 #include "opto/graphKit.hpp"
 #include "opto/idealKit.hpp"
 #include "opto/macro.hpp"
+#include "opto/narrowptrnode.hpp"

 ShenandoahBarrierSetC2* ShenandoahBarrierSetC2::bsc2() {
   return
reinterpret_cast<ShenandoahBarrierSetC2*>(BarrierSet::barrier_set()->barrier_set_c2());