vect: Pass reduc_info to get_initial_defs_for_reduction

vect: Pass reduc_info to get_initial_defs_for_reduction

This patch passes the reduc_info to get_initial_defs_for_reduction,
so that the function can get general information from there rather
than from the first SLP statement.  This isn't a win on its own,
but it becomes important with later patches.

gcc/
	* tree-vect-loop.c (get_initial_defs_for_reduction): Take the
	reduc_info as an additional parameter.
	(vect_transform_cycle_phi): Update accordingly.