irqdomain: Remove debugfs_file from struct irq_domain

There's no need to keep around a dentry pointer to a simple file that
debugfs itself can look up when we need to remove it from the system.
So simplify the code by deleting the variable and cleaning up the logic
around the debugfs file.

Cc: Marc Zyngier <maz@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/YCvYV53ZdzQSWY6w@kroah.com

include/linux/irqdomain.h

@@ -150,7 +150,6 @@ struct irq_domain_chip_generic;
  *      setting up one or more generic chips for interrupt controllers
  *      drivers using the generic chip library which uses this pointer.
  * @parent: Pointer to parent irq_domain to support hierarchy irq_domains
- * @debugfs_file: dentry for the domain debugfs file
  *
  * Revmap data, used internally by irq_domain
  * @revmap_direct_max_irq: The largest hwirq that can be set for controllers that
@@ -174,9 +173,6 @@ struct irq_domain {
 #ifdef	CONFIG_IRQ_DOMAIN_HIERARCHY
 	struct irq_domain *parent;
 #endif
-#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
-	struct dentry		*debugfs_file;
-#endif
 
 	/* reverse map data. The linear map gets appended to the irq_domain */
 	irq_hw_number_t hwirq_max;

kernel/irq/irqdomain.c

@@ -1898,16 +1898,15 @@ DEFINE_SHOW_ATTRIBUTE(irq_domain_debug);
 
 static void debugfs_add_domain_dir(struct irq_domain *d)
 {
-	if (!d->name || !domain_dir || d->debugfs_file)
+	if (!d->name || !domain_dir)
 		return;
-	d->debugfs_file = debugfs_create_file(d->name, 0444, domain_dir, d,
-					      &irq_domain_debug_fops);
+	debugfs_create_file(d->name, 0444, domain_dir, d,
+			    &irq_domain_debug_fops);
 }
 
 static void debugfs_remove_domain_dir(struct irq_domain *d)
 {
-	debugfs_remove(d->debugfs_file);
-	d->debugfs_file = NULL;
+	debugfs_remove(debugfs_lookup(d->name, domain_dir));
 }
 
 void __init irq_domain_debugfs_init(struct dentry *root)