irqchip/xtensa-mx: Fix initial IRQ affinity in non-SMP setup

When irq-xtensa-mx chip is used in non-SMP configuration its
irq_set_affinity callback is not called leaving IRQ affinity set empty.
As a result IRQ delivery does not work in that configuration.
Initialize IRQ affinity of the xtensa MX interrupt distributor to CPU 0
for all external IRQ lines.

Cc: [e-mail]
Signed-off-by: Max Filippov <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/irqchip/irq-xtensa-mx.c

···
 	.irq_set_affinity = xtensa_mx_irq_set_affinity,
 };
 
+static void __init xtensa_mx_init_common(struct irq_domain *root_domain)
+{
+	unsigned int i;
+
+	irq_set_default_host(root_domain);
+	secondary_init_irq();
+
+	/* Initialize default IRQ routing to CPU 0 */
+	for (i = 0; i < XCHAL_NUM_EXTINTERRUPTS; ++i)
+		set_er(1, MIROUT(i));
+}
+
 int __init xtensa_mx_init_legacy(struct device_node *interrupt_parent)
 {
 	struct irq_domain *root_domain =
 		irq_domain_add_legacy(NULL, NR_IRQS - 1, 1, 0,
 				&xtensa_mx_irq_domain_ops,
 				&xtensa_mx_irq_chip);
-	irq_set_default_host(root_domain);
-	secondary_init_irq();
+	xtensa_mx_init_common(root_domain);
 	return 0;
 }
 
···
 	struct irq_domain *root_domain =
 		irq_domain_add_linear(np, NR_IRQS, &xtensa_mx_irq_domain_ops,
 				&xtensa_mx_irq_chip);
-	irq_set_default_host(root_domain);
-	secondary_init_irq();
+	xtensa_mx_init_common(root_domain);
 	return 0;
 }
 IRQCHIP_DECLARE(xtensa_mx_irq_chip, "cdns,xtensa-mx", xtensa_mx_init);