middle-end/105083 - check prerequesites in scev_initialize

2022-05-03  Richard Biener  <rguenther@suse.de>

	PR middle-end/105083
	* tree-scalar-evolution.cc (scev_initialize): Verify we
	have appropriate loop state.
	* tree-ssa-dce.cc (perform_tree_ssa_dce): Re-order SCEV and
	loop init and finalization.