xen/arm: irq: Constify the first parameter of platform_get_irq_byname()

platform_get_irq_byname() is not meant to modify the parameter 'np'. So
constify it.

Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/include/asm/irq.h

@@ -89,7 +89,7 @@ int irq_set_type(unsigned int irq, unsigned int type);
 
 int platform_get_irq(const struct dt_device_node *device, int index);
 
-int platform_get_irq_byname(struct dt_device_node *np, const char *name);
+int platform_get_irq_byname(const struct dt_device_node *np, const char *name);
 
 void irq_set_affinity(struct irq_desc *desc, const cpumask_t *cpu_mask);
 

xen/arch/arm/irq.c

@@ -718,7 +718,7 @@ int platform_get_irq(const struct dt_device_node *device, int index)
     return irq;
 }
 
-int platform_get_irq_byname(struct dt_device_node *np, const char *name)
+int platform_get_irq_byname(const struct dt_device_node *np, const char *name)
 {
 	int index;