ARM: pxa: Constify irq_domain_ops

The irq_domain_ops are not modified by the driver and the irqdomain core
code accepts pointer to a const data.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
diff --git a/arch/arm/mach-pxa/irq.c b/arch/arm/mach-pxa/irq.c
index 89a7c06..98608c5 100644
--- a/arch/arm/mach-pxa/irq.c
+++ b/arch/arm/mach-pxa/irq.c
@@ -138,7 +138,7 @@
 	return 0;
 }
 
-static struct irq_domain_ops pxa_irq_ops = {
+static const struct irq_domain_ops pxa_irq_ops = {
 	.map    = pxa_irq_map,
 	.xlate  = irq_domain_xlate_onecell,
 };