PCI: Fix kerneldoc warnings

Fix kerneldoc warnings, e.g.,

  $ make W=1 drivers/pci/
  drivers/pci/ats.c:196: warning: Function parameter or member 'pdev' not described in 'pci_enable_pri'
  drivers/pci/ats.c:196: warning: Function parameter or member 'reqs' not described in 'pci_enable_pri'
  ...

Link: https://lore.kernel.org/r/20200729201224.26799-2-krzk@kernel.org
Link: https://lore.kernel.org/r/20200729201224.26799-3-krzk@kernel.org
Link: https://lore.kernel.org/r/20200729201224.26799-4-krzk@kernel.org
Link: https://lore.kernel.org/r/20200729201224.26799-5-krzk@kernel.org
Link: https://lore.kernel.org/r/20200729201224.26799-6-krzk@kernel.org
Link: https://lore.kernel.org/r/20200729201224.26799-7-krzk@kernel.org


Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>