PCI/EDR: Add edr_handle_event() comments

EDR documentation is a bit sketchy.  Add a couple comments to
edr_handle_event() about the devices involved.

Link: https://lore.kernel.org/r/20230407215259.GA3825733@bhelgaas


Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>