irqchip/loongson-liointc: Fix build warnings

Fix build warnings as below:

>> drivers/irqchip/irq-loongson-liointc.c:134:12: warning: no previous prototype for 'liointc_of_init' [-Wmissing-prototypes]
     134 | int __init liointc_of_init(struct device_node *node,
         |            ^~~~~~~~~~~~~~~

Fixes: dbb1522 ("irqchip: Add driver for Loongson I/O Local Interrupt Controller")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: chenhuacai

drivers/irqchip/irq-loongson-liointc.c

@@ -142,8 +142,8 @@ static void liointc_resume(struct irq_chip_generic *gc)
 
 static const char * const parent_names[] = {"int0", "int1", "int2", "int3"};
 
-int __init liointc_of_init(struct device_node *node,
-				struct device_node *parent)
+static int __init liointc_of_init(struct device_node *node,
+				  struct device_node *parent)
 {
 	struct irq_chip_generic *gc;
 	struct irq_domain *domain;