PCI: Fix kernel-doc build warning

Fix build error in kernel-doc notation:

  ../drivers/pci/pci.c:3479: ERROR: Unexpected indentation.

"::" tells the kernel-doc "reStructuredText" processor that the following
block is a literal block of some blob that should be kept as is.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
[bhelgaas: add hint about "::" meaning]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>