um: make PCI emulation driver init/exit static

The functions aren't used elsewhere, so they can be static.
Reported-by: kernel test robot <lkp@intel.com>
Fixes: 68f5d3f3 ("um: add PCI over virtio emulation driver")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/virt-pci.c

@@ -810,7 +810,7 @@ void *pci_root_bus_fwnode(struct pci_bus *bus)
 	return um_pci_fwnode;
 }
 
-int um_pci_init(void)
+static int um_pci_init(void)
 {
 	int err, i;
 
@@ -884,7 +884,7 @@ int um_pci_init(void)
 }
 module_init(um_pci_init);
 
-void um_pci_exit(void)
+static void um_pci_exit(void)
 {
 	unregister_virtio_driver(&um_pci_virtio_driver);
 	irq_domain_remove(um_pci_msi_domain);