PCI: Update the devres documentation regarding to pcim_*()

There were many changes to PCI core in scope of managed resources APIs.
Update documentation to list the current state of affairs.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20231006150634.3444251-1-andriy.shevchenko@linux.intel.com