powerpc: 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: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/sysdev/ipic.c b/arch/powerpc/sysdev/ipic.c
index b287337..d78f136 100644
--- a/arch/powerpc/sysdev/ipic.c
+++ b/arch/powerpc/sysdev/ipic.c
@@ -691,7 +691,7 @@
 	return 0;
 }
 
-static struct irq_domain_ops ipic_host_ops = {
+static const struct irq_domain_ops ipic_host_ops = {
 	.match	= ipic_host_match,
 	.map	= ipic_host_map,
 	.xlate	= irq_domain_xlate_onetwocell,