PCI/MSI: Get rid of externs in msi.h

Follow the style of <linux/pci.h>
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20221111122014.582175082@linutronix.de

drivers/pci/msi/msi.h

@@ -5,12 +5,12 @@
 
 #define msix_table_size(flags)	((flags & PCI_MSIX_FLAGS_QSIZE) + 1)
 
-extern int pci_msi_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
-extern void pci_msi_teardown_msi_irqs(struct pci_dev *dev);
+int pci_msi_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
+void pci_msi_teardown_msi_irqs(struct pci_dev *dev);
 
 #ifdef CONFIG_PCI_MSI_ARCH_FALLBACKS
-extern int pci_msi_legacy_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
-extern void pci_msi_legacy_teardown_msi_irqs(struct pci_dev *dev);
+int pci_msi_legacy_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
+void pci_msi_legacy_teardown_msi_irqs(struct pci_dev *dev);
 #else
 static inline int pci_msi_legacy_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
 {