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>

kernel/irq/handle.c

@@ -111,12 +111,11 @@ static void init_kstat_irqs(struct irq_desc *desc, int nr_desc, int nr)
 	}
 }
 
+#ifdef CONFIG_HAVE_SPARSE_IRQ
 /*
  * Protect the sparse_irqs_free freelist:
  */
 static DEFINE_SPINLOCK(sparse_irq_lock);
-
-#ifdef CONFIG_HAVE_SPARSE_IRQ
 static struct irq_desc *sparse_irqs_free;
 struct irq_desc *sparse_irqs;
 #endif