sched/fair: Consider capacity inversion in util_fits_cpu()

sched/fair: Consider capacity inversion in util_fits_cpu()

We do consider thermal pressure in util_fits_cpu() for uclamp_min only.
With the exception of the biggest cores which by definition are the max
performance point of the system and all tasks by definition should fit.

Even under thermal pressure, the capacity of the biggest CPU is the
highest in the system and should still fit every task. Except when it
reaches capacity inversion point, then this is no longer true.

We can handle this by using the inverted capacity as capacity_orig in
util_fits_cpu(). Which not only addresses the problem above, but also
ensure uclamp_max now considers the inverted capacity. Force fitting
a task when a CPU is in this adverse state will contribute to making the
thermal throttling last longer.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220804143609.515789-10-qais.yousef@arm.com