PCI: sysfs: Remove unused attribute groups

PCI: sysfs: Remove unused attribute groups

56c1af4606f0 ("PCI: Add sysfs max_link_speed/width,
current_link_speed/width, etc") added the following objects, but they are
unused, so remove them:

  pci_bridge_group
  pci_bridge_groups
  pcie_dev_group
  pcie_dev_groups

This fixes the following warnings from sparse:

  drivers/pci/pci-sysfs.c:1546:30: warning: symbol 'pci_bridge_groups' was not declared. Should it be static?
  drivers/pci/pci-sysfs.c:1555:30: warning: symbol 'pcie_dev_groups' was not declared. Should it be static?

Link: https://lore.kernel.org/r/20191016080324.12864-1-ben.dooks@codethink.co.uk
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>