irq_domain/powerpc: constify irq_domain_ops

Make all the irq_domain_ops structures in powerpc 'static const'

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Milton Miller <miltonm@bga.com>
Tested-by: Olof Johansson <olof@lixom.net>
diff --git a/arch/powerpc/platforms/52xx/media5200.c b/arch/powerpc/platforms/52xx/media5200.c
index 5db5cfb..17d91b7 100644
--- a/arch/powerpc/platforms/52xx/media5200.c
+++ b/arch/powerpc/platforms/52xx/media5200.c
@@ -136,7 +136,7 @@
 	return 0;
 }
 
-static struct irq_domain_ops media5200_irq_ops = {
+static const struct irq_domain_ops media5200_irq_ops = {
 	.map = media5200_irq_map,
 	.xlate = media5200_irq_xlate,
 };