arm: wire cpu-invariant accounting support up to the task scheduler

Commit 8cd5601c

 ("sched/fair: Convert arch_scale_cpu_capacity() from
weak function to #define") changed the wiring which now has to be done
by associating arch_scale_cpu_capacity with the actual implementation
provided by the architecture.

Define arch_scale_cpu_capacity to use the arch_topology "driver"
function topology_get_cpu_scale() for the task scheduler's cpu-invariant
accounting instead of the default arch_scale_cpu_capacity() in
kernel/sched/sched.h.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Tested-by: Juri Lelli <juri.lelli@arm.com>
Reviewed-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>