genirq: Make the cpuhotplug migration code less noisy

The original arm code has a pr_debug() statement for the case where
the irq chip has no set_affinity() callback. That's sufficient for
debugging and we really don't want to spam dmesg with useless warnings
for the normal case.

Fixes: f1e0bb0a: "genirq: Introduce generic irq migration for cpu hotunplug"
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Requested-by: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Yang Yingliang <yangyingliang@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Jiang Liu <jiang.liu@linux.intel.com>

kernel/irq/cpuhotplug.c

@@ -36,7 +36,7 @@ static bool migrate_one_irq(struct irq_desc *desc)
 
 	c = irq_data_get_irq_chip(d);
 	if (!c->irq_set_affinity) {
-		pr_warn_ratelimited("IRQ%u: unable to set affinity\n", d->irq);
+		pr_debug("IRQ%u: unable to set affinity\n", d->irq);
 	} else {
 		int r = irq_do_set_affinity(d, affinity, false);
 		if (r)