tree-optimization/103102 - fix error in vectorizer refactoring

tree-optimization/103102 - fix error in vectorizer refactoring

This fixes an oversight that caused vectorized epilogues to have
versioning for niters applied.

2021-11-08  Richard Biener  <rguenther@suse.de>

	* tree-vectorizer.h (vect_create_loop_vinfo): Add main_loop_info
	parameter.
	* tree-vect-loop.c (vect_create_loop_vinfo): Likewise.  Set
	LOOP_VINFO_ORIG_LOOP_INFO and conditionalize set of
	LOOP_VINFO_NITERS_ASSUMPTIONS.
	(vect_analyze_loop_1): Adjust.
	(vect_analyze_loop): Move loop constraint setting and
	SCEV/niter reset here from vect_create_loop_vinfo to perform
	it only once.
	(vect_analyze_loop_form): Move dumping of symbolic niters
	here from vect_create_loop_vinfo.