Fix the following sparse warning:

arch/x86/pci/xen.c:426:13: warning: symbol 'xen_msi_init' was not
declared. Should it be static?

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
---
 arch/x86/pci/xen.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 91220cc25854..0d06f12ccd74 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -423,7 +423,7 @@ int __init pci_xen_init(void)
 }
 
 #ifdef CONFIG_PCI_MSI
-void __init xen_msi_init(void)
+static void __init xen_msi_init(void)
 {
 	if (!disable_apic) {
 		/*
-- 
2.21.1