sched/fair: Detect capacity inversion

Check each performance domain to see if thermal pressure is causing its
capacity to be lower than another performance domain.

We assume that each performance domain has CPUs with the same
capacities, which is similar to an assumption made in energy_model.c

We also assume that thermal pressure impacts all CPUs in a performance
domain equally.

If there're multiple performance domains with the same capacity_orig, we
will trigger a capacity inversion if the domain is under thermal
pressure.

The new cpu_in_capacity_inversion() should help users to know when
information about capacity_orig are not reliable and can opt in to use
the inverted capacity as the 'actual' capacity_orig.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>