PCI: Remove "extern" from function declarations

We had an inconsistent mix of using and omitting the "extern" keyword
on function declarations in header files.  This removes them all.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/include/linux/pcieport_if.h b/include/linux/pcieport_if.h
index e6f91b1..9572669 100644
--- a/include/linux/pcieport_if.h
+++ b/include/linux/pcieport_if.h
@@ -62,7 +62,7 @@
 #define to_service_driver(d) \
 	container_of(d, struct pcie_port_service_driver, driver)
 
-extern int pcie_port_service_register(struct pcie_port_service_driver *new);
-extern void pcie_port_service_unregister(struct pcie_port_service_driver *new);
+int pcie_port_service_register(struct pcie_port_service_driver *new);
+void pcie_port_service_unregister(struct pcie_port_service_driver *new);
 
 #endif /* _PCIEPORT_IF_H_ */