tree-optimization/117698 - SLP vectorization and alignment

When SLP vectorizing we fail to mark the general alignment check
as irrelevant when using VMAT_STRIDED_SLP (the implementation checks
for itself) and when VMAT_INVARIANT the override isn't effective.

This results in extra FAILs on sparc which the following fixes.

	PR tree-optimization/117698
	* tree-vect-stmts.cc (get_group_load_store_type): Properly
	disregard alignment for VMAT_STRIDED_SLP and VMAT_INVARIANT.
	(vectorizable_load): Adjust guard for dumping whether we
	vectorize and unaligned access.
	(vectorizable_store): Likewise.