Reduce the number of STMT_VINFO_VECTYPE uses

Reduce the number of STMT_VINFO_VECTYPE uses

The following adjusts uses of STMT_VINFO_VECTYPE to look elsewhere
where obvious.

	* tree-vect-loop.cc (vect_analyze_loop_2): Get vectype
	from the SLP node.
	(vectorize_fold_left_reduction): Likewise.
	(vect_transform_reduction): Likewise.
	(vect_transform_cycle_phi): Likewise.
	(vect_transform_lc_phi): Likewise.
	* tree-vect-slp.cc (vect_analyze_slp): Likewise.
	* tree-vect-stmts.cc (vect_truncate_gather_scatter_offset):
	Pass in vectype and use that.
	(vect_use_strided_gather_scatters_p): Likewise.
	(get_group_load_store_type): Adjust.
	(vect_check_scalar_mask): We always have a SLP node.
	Use vectype from the SLP node.
	(vect_check_store_rhs): Likewise.
	(vect_build_one_gather_load_call): Pass in the vector type
	and use that.
	(vect_get_strided_load_store_ops): Likewise.
	(vectorizable_store): Adjust.
	(vectorizable_load): Use the vector type from the SLP node
	and adjust.