x86: Add dummy functions for compiling without IOAPIC

This patch adds IOAPIC dummy functions for compilation
with local APIC, but without IOAPIC.

The local variable ioapic_entries in enable_IR_x2apic()
does not need initialization anymore, since the dummy
returns NULL.

Signed-off-by: Henrik Kretzschmar <henne@nachtwindheim.de>
LKML-Reference: <1298385487-4708-4-git-send-email-henne@nachtwindheim.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 96e6809..f0e0798 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1449,7 +1449,7 @@
 void __init enable_IR_x2apic(void)
 {
 	unsigned long flags;
-	struct IO_APIC_route_entry **ioapic_entries = NULL;
+	struct IO_APIC_route_entry **ioapic_entries;
 	int ret, x2apic_enabled = 0;
 	int dmar_table_init_ret;