PCI: Fix kernel-doc formatting

Fix kernel-doc formatting throughout drivers/pci and related include files.
No change to functionality intended.

Check for warnings:

  $ find include drivers/pci -type f -path "*pci*.[ch]" | xargs scripts/kernel-doc -none

[bhelgaas: squashed to one commit]
Link: https://lore.kernel.org/r/20210509030237.368540-1-kw@linux.com
Link: https://lore.kernel.org/r/20210703151306.1922450-1-kw@linux.com
Link: https://lore.kernel.org/r/20210703151306.1922450-2-kw@linux.com
Link: https://lore.kernel.org/r/20210703151306.1922450-3-kw@linux.com
Link: https://lore.kernel.org/r/20210703151306.1922450-4-kw@linux.com
Link: https://lore.kernel.org/r/20210703151306.1922450-5-kw@linux.com


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