x86: build fix for "x86: fix C1E && nx6325 stability problem"

fix:

arch/x86/kernel/acpi/boot.c: In function ‘dmi_ignore_irq0_timer_override’:
arch/x86/kernel/acpi/boot.c:1443: error: implicit declaration of function ‘force_mask_ioapic_irq_2’
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/acpi/boot.c

@@ -37,6 +37,7 @@
 #include <asm/pgtable.h>
 #include <asm/io_apic.h>
 #include <asm/apic.h>
+#include <asm/genapic.h>
 #include <asm/io.h>
 #include <asm/mpspec.h>
 #include <asm/smp.h>