This fixes a hole that still allowed forwarding of TARGET_MEM_REF
addresses.

2020-05-25  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/95308
	* tree-ssa-forwprop.c (pass_forwprop::execute): Generalize
	test for TARGET_MEM_REFs.

	* g++.dg/torture/pr95308.C: New testcase.