RFR: Remove ShWB from formssel.cpp

[Roman Kennke]

We no longer expand ShenandoahWriteBarrier in the .ad files, and
therefore don't need the matchers in formssel.cpp:

diff --git a/src/hotspot/share/adlc/formssel.cpp
b/src/hotspot/share/adlc/formssel.cpp
--- a/src/hotspot/share/adlc/formssel.cpp
+++ b/src/hotspot/share/adlc/formssel.cpp
@@ -778,8 +778,7 @@
        !strcmp(_matrule->_rChild->_opType,"CompareAndExchangeN") ||

!strcmp(_matrule->_rChild->_opType,"ShenandoahCompareAndExchangeP") ||

!strcmp(_matrule->_rChild->_opType,"ShenandoahCompareAndExchangeN") ||
-       !strcmp(_matrule->_rChild->_opType,"ShenandoahReadBarrier") ||
-       !strcmp(_matrule->_rChild->_opType,"ShenandoahWriteBarrier")) )
return true;
+       !strcmp(_matrule->_rChild->_opType,"ShenandoahReadBarrier")))
return true;
   else if ( is_ideal_load() == Form::idealP )                return true;
   else if ( is_ideal_store() != Form::none  )                return true;

@@ -3504,7 +3503,7 @@
     "ClearArray",
     "GetAndSetB", "GetAndSetS", "GetAndAddI", "GetAndSetI", "GetAndSetP",
     "GetAndAddB", "GetAndAddS", "GetAndAddL", "GetAndSetL", "GetAndSetN",
-    "ShenandoahReadBarrier", "ShenandoahWriteBarrier",
+    "ShenandoahReadBarrier",
     "LoadBarrierSlowReg", "LoadBarrierWeakSlowReg"
   };
   int cnt = sizeof(needs_ideal_memory_list)/sizeof(char*);