tree-optimization/122225 - fix return stmt verification

tree-optimization/122225 - fix return stmt verification

The following fixes return stmt type verification by properly looking
at DECL_RESULT to decide whether that's by reference, not trying to
figure that from the actual argument.

	PR tree-optimization/122225
	* tree-cfg.cc (verify_gimple_return): Look at DECL_RESULT
	for DECL_BY_REFERENCE.