x86/xen: Make xen_msi_init() static and rename it to xen_hvm_msi_init()

The only user is in the same file and the name is too generic because this
function is only ever used for HVM domains.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Juergen Gross<jgross@suse.com>
Link: https://lore.kernel.org/r/20200826112333.234097629@linutronix.de

arch/x86/pci/xen.c

@@ -420,7 +420,7 @@ int __init pci_xen_init(void)
 }
 
 #ifdef CONFIG_PCI_MSI
-void __init xen_msi_init(void)
+static void __init xen_hvm_msi_init(void)
 {
 	if (!disable_apic) {
 		/*
@@ -460,7 +460,7 @@ int __init pci_xen_hvm_init(void)
 	 * We need to wait until after x2apic is initialized
 	 * before we can set MSI IRQ ops.
 	 */
-	x86_platform.apic_post_init = xen_msi_init;
+	x86_platform.apic_post_init = xen_hvm_msi_init;
 #endif
 	return 0;
 }