irqchip/loongarch-cpu: Fix a missing prototype warning

1, Rename loongarch_cpu_irq_of_init() to cpuintc_of_init() in order to
   keep the same style as the ACPI version.
2, Fix a missing prototype warning by adding a "static" modifier.

Fixes: 855d4ca4 ("irqchip: loongarch-cpu: add DT support")
Reported-by: kernel test robot <lkp@intel.com>
Cc: Peibao Liu <liupeibao@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221205044708.2054022-1-chenhuacai@loongson.cn

drivers/irqchip/irq-loongarch-cpu.c

@@ -93,7 +93,7 @@ static const struct irq_domain_ops loongarch_cpu_intc_irq_domain_ops = {
 };
 
 #ifdef CONFIG_OF
-int __init loongarch_cpu_irq_of_init(struct device_node *of_node,
+static int __init cpuintc_of_init(struct device_node *of_node,
 				struct device_node *parent)
 {
 	cpuintc_handle = of_node_to_fwnode(of_node);
@@ -107,8 +107,7 @@ int __init loongarch_cpu_irq_of_init(struct device_node *of_node,
 
 	return 0;
 }
-IRQCHIP_DECLARE(cpu_intc, "loongson,cpu-interrupt-controller",
-					loongarch_cpu_irq_of_init);
+IRQCHIP_DECLARE(cpu_intc, "loongson,cpu-interrupt-controller", cpuintc_of_init);
 #endif
 
 static int __init