8299022: Linux ppc64le and s390x build issues after JDK-8160404

Reviewed-by: mdoerr, lucy

Author: MBaesken

src/hotspot/cpu/ppc/assembler_ppc.hpp

@@ -95,7 +95,7 @@ class AddressLiteral {
 
  protected:
   // creation
-  AddressLiteral() : _address(NULL), _rspec(NULL) {}
+  AddressLiteral() : _address(NULL), _rspec() {}
 
  public:
   AddressLiteral(address addr, RelocationHolder const& rspec)

src/hotspot/cpu/s390/assembler_s390.hpp

@@ -295,7 +295,7 @@ class AddressLiteral {
 
  protected:
   // creation
-  AddressLiteral() : _address(NULL), _rspec(NULL) {}
+  AddressLiteral() : _address(NULL), _rspec() {}
 
  public:
   AddressLiteral(address addr, RelocationHolder const& rspec)