Remove hybrid SLP detection

Remove hybrid SLP detection

The following removes hybrid SLP detection - it existed as sanity
check that all stmts are covered by SLP, but it proved itself
incomplete at that.  Its job is taken by early terminating SLP
build when SLP discovery fails for one root and the hope that
we now do catch all of them.

	* tree-vectorizer.h (vect_relevant::hybrid): Remove.
	* tree-vect-loop.cc (vect_analyze_loop_2): Do not call
	vect_detect_hybrid_slp.
	* tree-vect-slp.cc (maybe_push_to_hybrid_worklist): Remove.
	(vect_detect_hybrid_slp): Likewise.