FROMLIST: sched: Relocate arch_scale_cpu_capacity

By default, arch_scale_cpu_capacity() is only visible from within the
kernel/sched folder. Relocate it to include/linux/sched/topology.h to
make it visible to other clients needing to know about the capacity of
CPUs, such as the Energy Model framework.

Change-Id: I144c7299e122201dbcadc431d55d0a6d24d90005
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
Message-Id: <20181016101513.26919-2-quentin.perret@arm.com>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>