pmdomain: core: Introduce dev_pm_genpd_rpm_always_on()

For some usecases a consumer driver requires its device to remain power-on
from the PM domain perspective during runtime. Using dev PM qos along with
the genpd governors, doesn't work for this case as would potentially
prevent the device from being runtime suspended too.

To support these usecases, let's introduce dev_pm_genpd_rpm_always_on() to
allow consumers drivers to dynamically control the behaviour in genpd for a
device that is attached to it.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/1738736156-119203-4-git-send-email-shawn.lin@rock-chips.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>