In Sema::InstantiateStaticDataMemberDefinition, pass the var decl to the consumer

just using ASTConsumer::HandleCXXStaticMemberVarInstantiation(), don't pass it with
ASTConsumer::HandleTopLevelDecl.

ASTConsumer::HandleTopLevelDecl is intended for user-written top-level decls;
a consumer can treat an instantiated static data member however it wants of course.

llvm-svn: 175976