powerpc: Print information about mapping hw irqs to virtual irqs

The irq remapping layer seems to cause some confusion when people
see a different irq number in /proc/interrupts vs the one they
request in their driver or DTS.

So have the irq remapping layer print out a message when we map an
irq. The message is only printed the first time the irq is mapped,
and it's KERN_DEBUG so most people won't see it.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/irq.c

@@ -672,11 +672,13 @@ unsigned int irq_create_mapping(struct irq_host *host,
 			return NO_IRQ;
 		}
 	}
-	pr_debug("irq: -> obtained virq %d\n", virq);
 
 	if (irq_setup_virq(host, virq, hwirq))
 		return NO_IRQ;
 
+	printk(KERN_DEBUG "irq: irq %lu on host %s mapped to virtual irq %u\n",
+		hwirq, host->of_node ? host->of_node->full_name : "null", virq);
+
 	return virq;
 }
 EXPORT_SYMBOL_GPL(irq_create_mapping);