fix warning: "x86: sparse_irq needs spin_lock in allocations"

caused by

commit a532e19680ada3b8579b81e67e76d3ebd19c340f
Author: Yinghai Lu <yhlu.kernel@gmail.com>
Date:   Wed Aug 20 20:46:25 2008 -0700

    x86: sparse_irq needs spin_lock in allocations

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>