sched: move load idx selection in find_idlest_group

load_idx is used in find_idlest_group but initialized in select_task_rq_fair
even when not used. The load_idx initialisation is moved in find_idlest_group
and the sd_flag replaces it in the function's args.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: flar2 <asegaert@gmail.com>