PCI: Fix comment typo, remove unnecessary !! in pci_is_pcie()

Use normal kernel-doc "Returns:" instead of "retrun"
Assignment to bool is always 1 or 0 so the !! isn't necessary.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>