x86, apic: streamline the ->multi_timer_check() quirk

only NUMAQ uses this quirk: to prevent the timer IRQ from being added
on secondary nodes.

All other genapic templates can have a NULL ->multi_timer_check()
callback.

Also, extend the generic code to treat a NULL pointer accordingly.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/mach-generic/default.c b/arch/x86/mach-generic/default.c
index 67f287f..6a21aa7 100644
--- a/arch/x86/mach-generic/default.c
+++ b/arch/x86/mach-generic/default.c
@@ -60,7 +60,7 @@
 
 	.ioapic_phys_id_map		= default_ioapic_phys_id_map,
 	.setup_apic_routing		= default_setup_apic_routing,
-	.multi_timer_check		= multi_timer_check,
+	.multi_timer_check		= NULL,
 	.apicid_to_node			= apicid_to_node,
 	.cpu_to_logical_apicid		= cpu_to_logical_apicid,
 	.cpu_present_to_apicid		= cpu_present_to_apicid,