sched/fair: Remove unused 'sd' parameter from scale_rt_capacity()

Since commit 8ec59c0f ("sched/topology: Remove unused 'sd'
parameter from arch_scale_cpu_capacity()") it is no longer needed.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20200603080304.16548-5-dietmar.eggemann@arm.com