x86: fix section mismatch warning - apic_x2apic_cluster

Impact: cleanup only, no functionality changed

WARNING: vmlinux.o(.data+0xbf88): Section mismatch in reference from the variable apic_x2apic_cluster to the function .init.text:x2apic_acpi_madt_oem_check()
The variable apic_x2apic_cluster references
the function __init x2apic_acpi_madt_oem_check()
Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/genx2apic_cluster.c

@@ -12,7 +12,7 @@
 
 DEFINE_PER_CPU(u32, x86_cpu_to_logical_apicid);
 
-static int __init x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
+static int x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
 {
 	if (cpu_has_x2apic)
 		return 1;