genirq/debugfs: Reinstate full OF path for domain name

On a DT based system, we use the of_node full name to name the
corresponding irq domain. We expect that name to be unique, so so that
domains with the same base name won't clash (this happens on multi-node
topologies, for example).

Since a7e4cfb0a7 ("of/fdt: only store the device node basename in
full_name"), of_node_full_name() lies and only returns the basename. This
breaks the above requirement, and we end-up with only a subset of the
domains in /sys/kernel/debug/irq/domains.

Let's reinstate the feature by using the fancy new %pOF format specifier,
which happens to do the right thing.

Fixes: a7e4cfb0a7 ("of/fdt: only store the device node basename in full_name")
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20181001100522.180054-3-marc.zyngier@arm.com

kernel/irq/irqdomain.c

@@ -183,7 +183,7 @@ struct irq_domain *__irq_domain_add(struct fwnode_handle *fwnode, int size,
 		 * unhappy about. Replace them with ':', which does
 		 * the trick and is not as offensive as '\'...
 		 */
-		name = kstrdup(of_node_full_name(of_node), GFP_KERNEL);
+		name = kasprintf(GFP_KERNEL, "%pOF", of_node);
 		if (!name) {
 			kfree(domain);
 			return NULL;