irqchip/bcm7038-l1: Hide cpu offline callback when building for !SMP

When compiling bmips with SMP disabled, the build fails with:

drivers/irqchip/irq-bcm7038-l1.o: In function `bcm7038_l1_cpu_offline':
drivers/irqchip/irq-bcm7038-l1.c:242: undefined reference to `irq_set_affinity_locked'
make[5]: *** [vmlinux] Error 1

Fix this by adding and setting bcm7038_l1_cpu_offline only when actually
compiling for SMP. It wouldn't have been used anyway, as it requires
CPU_HOTPLUG, which in turn requires SMP.

Fixes: 34c535793b ("irqchip/bcm7038-l1: Implement irq_cpu_offline() callback")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/irq-bcm7038-l1.c

@@ -217,6 +217,7 @@ static int bcm7038_l1_set_affinity(struct irq_data *d,
 	return 0;
 }
 
+#ifdef CONFIG_SMP
 static void bcm7038_l1_cpu_offline(struct irq_data *d)
 {
 	struct cpumask *mask = irq_data_get_affinity_mask(d);
@@ -241,6 +242,7 @@ static void bcm7038_l1_cpu_offline(struct irq_data *d)
 	}
 	irq_set_affinity_locked(d, &new_affinity, false);
 }
+#endif
 
 static int __init bcm7038_l1_init_one(struct device_node *dn,
 				      unsigned int idx,
@@ -293,7 +295,9 @@ static struct irq_chip bcm7038_l1_irq_chip = {
 	.irq_mask		= bcm7038_l1_mask,
 	.irq_unmask		= bcm7038_l1_unmask,
 	.irq_set_affinity	= bcm7038_l1_set_affinity,
+#ifdef CONFIG_SMP
 	.irq_cpu_offline	= bcm7038_l1_cpu_offline,
+#endif
 };
 
 static int bcm7038_l1_map(struct irq_domain *d, unsigned int virq,