PM: domains: Fixup QoS latency measurements for IRQ safe devices in genpd

When an IRQ safe device is attached to a non-IRQ safe PM domain, genpd
needs to prevent the PM domain from being powered off. However, genpd still
allows the device to be runtime suspended/resumed, hence it's also
reasonable to think that a governor may be used to validate the QoS latency
constraints.

Unfortunately, genpd_runtime_resume() treats the configuration above, as a
reason to skip measuring the QoS resume latency for the device. This is a
legacy behaviour that was earlier correct, but should have been changed
when genpd was transformed into its current behaviour around how it manages
IRQ safe devices. Luckily, there's no report about problems, so let's just
fixup the behaviour.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>