i3c: mipi-i3c-hci-pci: Add optional ability to manage child runtime PM

i3c: mipi-i3c-hci-pci: Add optional ability to manage child runtime PM

Some platforms implement the MIPI I3C HCI Multi-Bus Instance capability,
where a single parent device hosts multiple I3C controller instances.  In
such designs, the parent - not the individual child instances - may need to
coordinate runtime PM so that all controllers runtime PM callbacks are
invoked in a controlled and synchronized manner.

For example, if the parent enables IBI-wakeup when transitioning into a
low-power state, every bus instance must remain able to receive IBIs up
until that point.  This requires deferring the individual controllers'
runtime suspend callbacks (which disable bus activity) until the parent
decides it is safe for all instances to suspend together.

To support this usage model:

  * Add runtime PM and system PM callbacks in the PCI driver to invoke
    the mipi-i3c-hci driver's runtime PM callbacks for each instance.

  * Introduce a driver-data flag, control_instance_pm, which opts into
    the new parent-managed PM behaviour.

  * Ensure the callbacks are only used when the corresponding instance is
    operational at suspend time.  This is reliable because the operational
    state cannot change while the parent device is undergoing a PM
    transition, and PCI always performs a runtime resume before system
    suspend on current configurations, so that suspend and resume alternate
    irrespective of whether it is runtime or system PM.

By that means, parent-managed runtime PM coordination for multi-instance
MIPI I3C HCI PCI devices is provided without altering existing behaviour on
platforms that do not require it.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260306085338.62955-5-adrian.hunter@intel.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>