sched/cpufreq: Modify aggregate utilization to always include blocked FAIR utilization

Since the refactoring introduced by:

   commit 8f111bc357aa ("cpufreq/schedutil: Rewrite CPUFREQ_RT support")

we aggregate FAIR utilization only if this class has runnable tasks.

This was mainly due to avoid the risk to stay on an high frequency just
because of the blocked utilization of a CPU not being properly decayed
while the CPU was idle.

However, since:

   commit 31e77c93e432 ("sched/fair: Update blocked load when newly idle")

the FAIR blocked utilization is properly decayed also for IDLE CPUs.

This allows us to use the FAIR blocked utilization as a safe mechanism
to gracefully reduce the frequency only if no FAIR tasks show up on a
CPU for a reasonable period of time.

Moreover, we also reduce the frequency drops of CPUs running periodic
tasks which, depending on the task periodicity and the time required
for a frequency switch, was increasing the chances to introduce some
undesirable performance variations.

Reported-by: Vincent Guittot <[email protected]>
Tested-by: Vincent Guittot <[email protected]>
Signed-off-by: Patrick Bellasi <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Acked-by: Viresh Kumar <[email protected]>
Acked-by: Vincent Guittot <[email protected]>
Cc: Dietmar Eggemann <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Morten Rasmussen <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rafael J . Wysocki <[email protected]>
Cc: Steve Muckle <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

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