pci_init_capabilities() is the only caller and doesn't use the return
value. So let's change the return type to void.

Link: https://lore.kernel.org/r/663ec440-8375-1459-ddb4-98ea76e75917@gmail.comSigned-off-by: NHeiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>