sched/topology: Remove redundant cpumask_and() in init_overlap_sched_group()

mask is built in build_balance_mask() by for_each_cpu(i, sg_span), so
it must be a subset of sched_group_span(sg).

So the cpumask_and() call is redundant - remove it.

[ mingo: Adjusted the changelog a bit. ]

Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Link: https://lore.kernel.org/r/20210325023140.23456-1-song.bao.hua@hisilicon.com