sched_tp: Add cpu_capacity trace events

...
[000] .Ns3 185.489841: sched_cpu_capacity: cpu=0 capacity=437 capacity_orig=446
[002] ..s1 185.501802: sched_cpu_capacity: cpu=2 capacity=999 capacity_orig=1024
[003] ..s3 185.517837: sched_cpu_capacity: cpu=3 capacity=438 capacity_orig=446
[002] ..s1 185.529794: sched_cpu_capacity: cpu=2 capacity=999 capacity_orig=1024
[001] ..s1 185.545789: sched_cpu_capacity: cpu=1 capacity=1011 capacity_orig=1024
[004] .Ns1 185.545837: sched_cpu_capacity: cpu=4 capacity=439 capacity_orig=446
...

Use arch_scale_cpu_capacity() instead of rq->cpu_capacity_orig because
there is a patch further up the stack which removes the latter.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>