tree-optimization/117556 - SLP of live stmts from load-lanes

The following fixes SLP live lane generation for load-lanes which
fails to analyze for gcc.dg/vect/vect-live-slp-3.c because the
VLA division doesn't work out but it would also wrongly use the
transposed vector defs I think.  The following properly disables
the actual load-lanes SLP node from live lane processing and instead
relies on the SLP permute node representing the live lane where we
can use extract-last to extract the last lane.  This also fixes
the reported Ada miscompile.

	PR tree-optimization/117556
	PR tree-optimization/117553
	* tree-vect-stmts.cc (vect_analyze_stmt): Do not analyze
	the SLP load-lanes node for live lanes, but only the
	permute node.
	(vect_transform_stmt): Likewise for the transform.

	* gcc.dg/vect/vect-live-slp-3.c: Expect us to SLP even for
	VLA vectors (in single-lane mode).