genirq/irq_sim: Check the return value of irq_sim_init() for error codes

As discussed with Marc Zyngier: irq_sim_init() and its devres variant
should return the base of the allocated interrupt range on success rather
than 0.

Make devm_irq_sim_init() check for an error code. This is a preparatory
change for modifying irq_sim_init() itself.
Signed-off-by: NBartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/20180304121018.640-3-brgl@bgdev.pl

kernel/irq/irq_sim.c

@@ -124,7 +124,7 @@ int devm_irq_sim_init(struct device *dev, struct irq_sim *sim,
 		return -ENOMEM;
 
 	rv = irq_sim_init(sim, num_irqs);
-	if (rv) {
+	if (rv < 0) {
 		devres_free(dr);
 		return rv;
 	}