sparseirq: set lock_class for legacy irq when sparse_irq is selected

Impact: add lockdep annotation to legacy IRQ descs

Warnings resulting out of this were not seen in practice, but it's prudent
to initialize the legacy descriptors to the lock class as well, symmetric
to how we do it with other descriptors.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/irq/handle.c

@@ -145,6 +145,7 @@ int __init early_irq_init(void)
 	for (i = 0; i < legacy_count; i++) {
 		desc[i].irq = i;
 		desc[i].kstat_irqs = kstat_irqs_legacy[i];
+		lockdep_set_class(&desc[i].lock, &irq_desc_lock_class);
 
 		irq_desc_ptrs[i] = desc + i;
 	}