i3c: mipi-i3c-hci: Allow parent to manage 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:

* Export the low-level runtime PM suspend and resume helpers so that
the parent can explicitly invoke them.

* Add a new quirk, HCI_QUIRK_RPM_PARENT_MANAGED, allowing platforms to
bypass per-instance runtime PM callbacks and delegate control to the
parent device.

* Move DEFAULT_AUTOSUSPEND_DELAY_MS into the header so it can be shared
by parent-managed PM implementations.

The new quirk allows platforms with multi-bus parent-managed PM
infrastructure to correctly coordinate runtime PM across all I3C HCI
instances.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260306085338.62955-4-adrian.hunter@intel.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>