irq_domain: remove NO_IRQ from irq domain code

zero always means no irq when using irq domains. Get rid of the NO_IRQ
references.

Signed-off-by: Grant Likely <[e-mail]>
Cc: Rob Herring <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Milton Miller <[e-mail]>
Tested-by: Olof Johansson <[e-mail]>

kernel/irq/irqdomain.c

···
 	case IRQ_DOMAIN_MAP_LINEAR:
 		rmap = (unsigned int *)(host + 1);
 		for (i = 0; i < revmap_arg; i++)
-			rmap[i] = NO_IRQ;
+			rmap[i] = 0;
 		host->revmap_data.linear.size = revmap_arg;
 		host->revmap_data.linear.revmap = rmap;
 		break;
···
 	WARN_ON(host->revmap_type != IRQ_DOMAIN_MAP_NOMAP);
 
 	virq = irq_alloc_desc_from(1, 0);
-	if (virq == NO_IRQ) {
+	if (!virq) {
 		pr_debug("irq: create_direct virq allocation failed\n");
-		return NO_IRQ;
+		return 0;
 	}
 	if (virq >= irq_virq_count) {
 		pr_err("ERROR: no free irqs available below %i maximum\n",
···
 
 	if (irq_setup_virq(host, virq, virq)) {
 		irq_free_desc(virq);
-		return NO_IRQ;
+		return 0;
 	}
 
 	return virq;
···
 		printk(KERN_WARNING "irq_create_mapping called for"
 		       " NULL host, hwirq=%lx\n", hwirq);
 		WARN_ON(1);
-		return NO_IRQ;
+		return 0;
 	}
 	pr_debug("irq: -> using host @%p\n", host);
 
 	/* Check if mapping already exists */
 	virq = irq_find_mapping(host, hwirq);
-	if (virq != NO_IRQ) {
+	if (virq) {
 		pr_debug("irq: -> existing mapping on virq %d\n", virq);
 		return virq;
 	}
···
 		/* Handle legacy */
 		virq = (unsigned int)hwirq;
 		if (virq == 0 || virq >= NUM_ISA_INTERRUPTS)
-			return NO_IRQ;
+			return 0;
 		return virq;
 	} else {
 		/* Allocate a virtual interrupt number */
···
 		virq = irq_alloc_desc_from(hint, 0);
 		if (!virq)
 			virq = irq_alloc_desc_from(1, 0);
-		if (virq == NO_IRQ) {
+		if (!virq) {
 			pr_debug("irq: -> virq allocation failed\n");
-			return NO_IRQ;
+			return 0;
 		}
 	}
 
 	if (irq_setup_virq(host, virq, hwirq)) {
 		if (host->revmap_type != IRQ_DOMAIN_MAP_LEGACY)
 			irq_free_desc(virq);
-		return NO_IRQ;
+		return 0;
 	}
 
 	pr_debug("irq: irq %lu on host %s mapped to virtual irq %u\n",
···
 	if (host == NULL) {
 		printk(KERN_WARNING "irq: no irq host found for %s !\n",
 		       controller->full_name);
-		return NO_IRQ;
+		return 0;
 	}
 
 	/* If host has no translation, then we assume interrupt line */
···
 	else {
 		if (host->ops->xlate(host, controller, intspec, intsize,
 				     &hwirq, &type))
-			return NO_IRQ;
+			return 0;
 	}
 
 	/* Create mapping */
 	virq = irq_create_mapping(host, hwirq);
-	if (virq == NO_IRQ)
+	if (!virq)
 		return virq;
 
 	/* Set type if specified and different than the current one */
···
 	struct irq_domain *host;
 	irq_hw_number_t hwirq;
 
-	if (virq == NO_IRQ || !irq_data)
+	if (!virq || !irq_data)
 		return;
 
 	host = irq_data->domain;
···
 	switch(host->revmap_type) {
 	case IRQ_DOMAIN_MAP_LINEAR:
 		if (hwirq < host->revmap_data.linear.size)
-			host->revmap_data.linear.revmap[hwirq] = NO_IRQ;
+			host->revmap_data.linear.revmap[hwirq] = 0;
 		break;
 	case IRQ_DOMAIN_MAP_TREE:
 		mutex_lock(&revmap_trees_mutex);
···
 	if (host == NULL)
 		host = irq_default_host;
 	if (host == NULL)
-		return NO_IRQ;
+		return 0;
 
 	/* legacy -> bail early */
 	if (host->revmap_type == IRQ_DOMAIN_MAP_LEGACY)
···
 		if (i >= irq_virq_count)
 			i = 1;
 	} while(i != hint);
-	return NO_IRQ;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(irq_find_mapping);
 
···
 	if (WARN_ON(host->revmap_type != IRQ_DOMAIN_MAP_TREE))
 		return;
 
-	if (virq != NO_IRQ) {
+	if (virq) {
 		mutex_lock(&revmap_trees_mutex);
 		radix_tree_insert(&host->revmap_data.tree, hwirq, irq_data);
 		mutex_unlock(&revmap_trees_mutex);
···
 		return irq_find_mapping(host, hwirq);
 
 	/* Fill up revmap with slow path if no mapping found */
-	if (unlikely(revmap[hwirq] == NO_IRQ))
+	if (unlikely(!revmap[hwirq]))
 		revmap[hwirq] = irq_find_mapping(host, hwirq);
 
 	return revmap[hwirq];