MAINTAINERS: Update PCI subsystem information

Update the following information related to the PCI subsystem which
includes the PCI drivers, PCI native host bridge and endpoint drivers,
and the PCI endpoint sub-system:

 - Sort fields as per preferred order
 - Sort files in the alphabetical order
 - Update old Patchwork URLs
 - Update Git repository for the PCI endpoint subsystem
 - Add Bugzilla link
 - Add link to the official IRC channel
 - Add files "drivers/pci/pci-bridge-emul.{c,h}" to the right
   section so that proper ownership is returned for both files
   from the get_maintainer.pl script

Link: https://lore.kernel.org/r/20211027105041.24087-1-kw@linux.com


Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>