FROMLIST: sched: use pelt for scale_rt_capacity()

FROMLIST: sched: use pelt for scale_rt_capacity()

The utilization of the CPU by rt, dl and interrupts are now tracked with
PELT so we can use these metrics instead of rt_avg to evaluate the remaining
capacity available for cfs class.

scale_rt_capacity() behavior has been changed and now returns the remaining
capacity available for cfs instead of a scaling factor because rt, dl and
interrupt provide now absolute utilization value.

The same formula as schedutil is used:
  irq util_avg + (1 - irq util_avg / max capacity ) * /Sum rq util_avg
but the implementation is different because it doesn't return the same value
and doesn't benefit of the same optimization

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
[ - Fixed issue with the max freq capping in update_cpu_capacity()
  - Fixed compile warning for !CONFIG_IRQ_TIME_ACCOUNTING ]
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
Change-Id: I4a25191bba3b7b19d075f5a95845caebdbcb9c24