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

fix:

 arch/x86/kernel/built-in.o: In function `dmi_ignore_irq0_timer_override':
 boot.c:(.init.text+0x3ea4): undefined reference to `force_mask_ioapic_irq_2'

Signed-off-by: Ingo Molnar <mingo@elte.hu>