vect: Move slp_perm checking into get_load_store_type.

vect: Move slp_perm checking into get_load_store_type.

This moves the setting of slp_perm, checking of basic-block SLP gaps, as
well as the final check for perm_ok to get_load_store_type.
Also, slp_perm is moved to ls_data.

gcc/ChangeLog:

	* tree-vect-stmts.cc (get_load_store_type): Add load-permutation
	checks and setting of slp_perm.
	(vectorizable_store): Remove perm_ok argument.
	(vectorizable_load): Ditto and replace slp_perm by ls.slp_perm.
	* tree-vectorizer.h (struct vect_load_store_data): Add slp_perm.