i3c: mipi-i3c-hci-pci: Add System Suspend support

i3c: mipi-i3c-hci-pci: Add System Suspend support

Assign the driver PM operations pointer, which is necessary for the PCI
subsystem to put the device into a low power state.  Refer to
pci_pm_suspend_noirq() which bails out if the pointer is NULL, before
it has the opportunity to call pci_prepare_to_sleep().

No other actions are necessary as the mipi-i3c-hci driver takes care of
controller state.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260123063325.8210-4-adrian.hunter@intel.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>