regmap: irq: Set lockdep class for hierarchical IRQ domains

Lockdep gives a false positive splat as it can't distinguish the lock
which is taken by different IRQ descriptors from different IRQ chips
that are organized in a way of a hierarchy:

======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc5-next-20241101-00148-g9fabf8160b53 #562 Tainted: G W
------------------------------------------------------
modprobe/141 is trying to acquire lock:
ffff899446947868 (intel_soc_pmic_bxtwc:502:(&bxtwc_regmap_config)->lock){+.+.}-{4:4}, at: regmap_update_bits_base+0x33/0x90

but task is already holding lock:
ffff899446947c68 (&d->lock){+.+.}-{4:4}, at: __setup_irq+0x682/0x790

which lock already depends on the new lock.

-> #3 (&d->lock){+.+.}-{4:4}:
-> #2 (&desc->request_mutex){+.+.}-{4:4}:
-> #1 (ipclock){+.+.}-{4:4}:
-> #0 (intel_soc_pmic_bxtwc:502:(&bxtwc_regmap_config)->lock){+.+.}-{4:4}:

Chain exists of:
intel_soc_pmic_bxtwc:502:(&bxtwc_regmap_config)->lock --> &desc->request_mutex --> &d->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&d->lock);
lock(&desc->request_mutex);
lock(&d->lock);
lock(intel_soc_pmic_bxtwc:502:(&bxtwc_regmap_config)->lock);

*** DEADLOCK ***

3 locks held by modprobe/141:
#0: ffff8994419368f8 (&dev->mutex){....}-{4:4}, at: __driver_attach+0xf6/0x250
#1: ffff89944690b250 (&desc->request_mutex){+.+.}-{4:4}, at: __setup_irq+0x1a2/0x790
#2: ffff899446947c68 (&d->lock){+.+.}-{4:4}, at: __setup_irq+0x682/0x790

Set a lockdep class when we map the IRQ so that it doesn't warn about
a lockdep bug that doesn't exist.

Fixes: 4af8be67fd99 ("regmap: Convert regmap_irq to use irq_domain")
Signed-off-by: Andy Shevchenko <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/base/regmap/regmap-irq.c

···
 		return IRQ_NONE;
 }
 
+static struct lock_class_key regmap_irq_lock_class;
+static struct lock_class_key regmap_irq_request_class;
+
 static int regmap_irq_map(struct irq_domain *h, unsigned int virq,
 			  irq_hw_number_t hw)
 {
 	struct regmap_irq_chip_data *data = h->host_data;
 
 	irq_set_chip_data(virq, data);
+	irq_set_lockdep_class(virq, &regmap_irq_lock_class, &regmap_irq_request_class);
 	irq_set_chip(virq, &data->irq_chip);
 	irq_set_nested_thread(virq, 1);
 	irq_set_parent(virq, data->irq);