[vect] Keep track of DR_OFFSET advance in dr_vec_info rather than data_reference

gcc/ChangeLog:
2020-01-10  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	* tree-vect-data-refs.c (vect_create_addr_base_for_vector_ref): Use
	get_dr_vinfo_offset
	* tree-vect-loop.c (update_epilogue_loop_vinfo):  Remove orig_drs_init
	parameter and its use to reset DR_OFFSET's.
	(vect_transform_loop): Remove orig_drs_init argument.
	* tree-vect-loop-manip.c (vect_update_init_of_dr): Update the offset
	member of dr_vec_info rather than the offset of the associated
	data_reference's innermost_loop_behavior.
	(vect_update_init_of_dr): Pass dr_vec_info instead of data_reference.
	(vect_do_peeling): Remove orig_drs_init parameter and its construction.
	* tree-vect-stmts.c (check_scan_store): Replace use of DR_OFFSET with
	get_dr_vinfo_offset.
	(vectorizable_store): Likewise.
	(vectorizable_load): Likewise.

From-SVN: r280107