sched/fair: jump to max OPP when crossing UP threshold

Since the true utilization of a long running task is not detectable
while it is running and might be bigger than the current cpu capacity,
create the maximum cpu capacity head room by requesting the maximum
cpu capacity once the cpu usage plus the capacity margin exceeds the
current capacity. This is also done to try to harm the performance of
a task the least.

Original fair-class only version authored by Juri Lelli
<juri.lelli@arm.com>.

Change-Id: I42c4eda2a98e8e73dbd3e1c41d1b81a6e3e37f2e
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Steve Muckle <smuckle@linaro.org>
(am from https://patchwork.kernel.org/patch/7804971/

)
Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>