Remove empty non-virtual destructors or mark them =default when non-public

These add no value but can make a class non-trivially copyable. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234688 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineRegionInfo.h

@@ -57,8 +57,6 @@ public:
 
   }
 
-  ~MachineRegionNode() { }
-
   bool operator==(const MachineRegion &RN) const {
     return this == reinterpret_cast<const MachineRegionNode*>(&RN);
   }