x86: Move alloc_desk_mask variables inside ifdef

They are only useful with CONFIG_CPUMASK_OFFSTACK
Avoids hundreds of warnings with a gcc 4.6 -Wall build.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/irq.h

@@ -439,12 +439,12 @@ extern int set_irq_msi(unsigned int irq, struct msi_desc *entry);
 static inline bool alloc_desc_masks(struct irq_desc *desc, int node,
 							bool boot)
 {
+#ifdef CONFIG_CPUMASK_OFFSTACK
 	gfp_t gfp = GFP_ATOMIC;
 
 	if (boot)
 		gfp = GFP_NOWAIT;
 
-#ifdef CONFIG_CPUMASK_OFFSTACK
 	if (!alloc_cpumask_var_node(&desc->affinity, gfp, node))
 		return false;