[aarch64-port-dev ] RFR [sh/8u]: Revert accidental OpSpinWait matching

[Aleksey Shipilev]

We have a weird difference between our sh/jdk8 development repo and aarch64-port-jdk8u-shenandoah
integration forest: it has a little branch that "matches" OpSpinWait, even though there is no such
node in 8u at all -- that feature came in JDK 9. This had accidentally leaked during previous merges.

So, we want to push this to aarch64-port/jdk8u-shenandoah:

diff -r 966a10251cb4 src/share/vm/adlc/formssel.cpp
--- a/src/share/vm/adlc/formssel.cpp	Wed Mar 21 20:00:58 2018 +0000
+++ b/src/share/vm/adlc/formssel.cpp	Thu Mar 22 12:03:44 2018 +0100
@@ -4066,8 +4066,7 @@
     !strcmp(_opType,"StoreFence") ||
     !strcmp(_opType,"MemBarVolatile") ||
     !strcmp(_opType,"MemBarCPUOrder") ||
-    !strcmp(_opType,"MemBarStoreStore") ||
-    !strcmp(_opType, "OnSpinWait");
+    !strcmp(_opType,"MemBarStoreStore");
 }

 bool MatchRule::is_ideal_loadPC() const {

Testing: x86_64 build, hotspot_gc_shenandoah

Thanks,
-Aleksey