cpuidle: psci: Correct the domain-idlestate statistics in debugfs

When trying to enter a domain-idlestate, we may occasionally fail to enter
the state, which is informed to us by psci_cpu_suspend_enter() returning an
error-code. In these cases, our corresponding genpd->power_off() callback
has already returned zero to indicate success, leading to getting
in-correct domain-idlestate statistics in debugfs for the genpd in
question.

Let's fix this by making use of the new pm_genpd_inc_rejected() helper, as
it allows us to correct the domain-idlestate statistics for this type of
scenario.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20250314100103.1294715-4-ulf.hansson@linaro.org