sched/topology: Fix build_sched_groups() comment

sched/topology: Fix build_sched_groups() comment

The comment was introduced (pre 2.6.12) by:

  8a7a2318dc07 ("[PATCH] sched: consolidate sched domains")

and referred to sched_group->cpu_power. This was folded into
sched_group->sched_group_power in

  commit 9c3f75cbd144 ("sched: Break out cpu_power from the sched_group structure")

The comment was then updated in:

  ced549fa5fc1 ("sched: Remove remaining dubious usage of "power"")

but should have replaced "sg->cpu_capacity" with
"sg->sched_group_capacity". Do that now.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Cc: Dietmar.Eggemann@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: morten.rasmussen@arm.com
Cc: qais.yousef@arm.com
Link: http://lkml.kernel.org/r/20190409173546.4747-3-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>