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>

include/linux/msi.h

@@ -13,14 +13,14 @@ struct msi_msg {
 /* Helper functions */
 struct irq_data;
 struct msi_desc;
-extern void mask_msi_irq(struct irq_data *data);
-extern void unmask_msi_irq(struct irq_data *data);
-extern void __read_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
-extern void __get_cached_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
-extern void __write_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
-extern void read_msi_msg(unsigned int irq, struct msi_msg *msg);
-extern void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg);
-extern void write_msi_msg(unsigned int irq, struct msi_msg *msg);
+void mask_msi_irq(struct irq_data *data);
+void unmask_msi_irq(struct irq_data *data);
+void __read_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
+void __get_cached_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
+void __write_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
+void read_msi_msg(unsigned int irq, struct msi_msg *msg);
+void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg);
+void write_msi_msg(unsigned int irq, struct msi_msg *msg);
 
 struct msi_desc {
 	struct {
@@ -54,9 +54,8 @@ struct msi_desc {
  */
 int arch_setup_msi_irq(struct pci_dev *dev, struct msi_desc *desc);
 void arch_teardown_msi_irq(unsigned int irq);
-extern int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
-extern void arch_teardown_msi_irqs(struct pci_dev *dev);
-extern int arch_msi_check_device(struct pci_dev* dev, int nvec, int type);
-
+int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
+void arch_teardown_msi_irqs(struct pci_dev *dev);
+int arch_msi_check_device(struct pci_dev* dev, int nvec, int type);
 
 #endif /* LINUX_MSI_H */