PM: domains: Allow devices attached to genpd to be managed by HW

Some power-domains may be capable of relying on the HW to control the power
for a device that's hooked up to it. Typically, for these kinds of
configurations the consumer driver should be able to change the behavior of
power domain at runtime, control the power domain in SW mode for certain
configurations and handover the control to HW mode for other usecases.

To allow a consumer driver to change the behaviour of the PM domain for its
device, let's provide a new function, dev_pm_genpd_set_hwmode(). Moreover,
let's add a corresponding optional genpd callback, ->set_hwmode_dev(),
which the genpd provider should implement if it can support switching
between HW controlled mode and SW controlled mode. Similarly, add the
dev_pm_genpd_get_hwmode() to allow consumers to read the current mode and
its corresponding optional genpd callback, ->get_hwmode_dev(), which the
genpd provider can also implement to synchronize the initial HW mode
state in genpd_add_device() by reading back the mode from the hardware.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Jagadeesh Kona <quic_jkona@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Dhruva Gole <d-gole@ti.com>
Reviewed-by: Taniya Das <quic_tdas@quicinc.com>
Link: https://lore.kernel.org/r/20240624044809.17751-2-quic_jkona@quicinc.com