irq_domain: constify irq_domain_ops

Make irq_domain_ops pointer a constant to make it safer for multiple
instances to share the same ops pointer and change the irq_domain code
so that it does not modify the ops.

v4: Fix mismatched type reference in powerpc code

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Milton Miller <miltonm@bga.com>
Tested-by: Olof Johansson <olof@lixom.net>
diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index ea58f36..5245488 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -106,7 +106,7 @@
 		} linear;
 		struct radix_tree_root tree;
 	} revmap_data;
-	struct irq_domain_ops *ops;
+	const struct irq_domain_ops *ops;
 	void *host_data;
 	irq_hw_number_t inval_irq;
 
@@ -119,17 +119,17 @@
 					 unsigned int size,
 					 unsigned int first_irq,
 					 irq_hw_number_t first_hwirq,
-					 struct irq_domain_ops *ops,
+					 const struct irq_domain_ops *ops,
 					 void *host_data);
 struct irq_domain *irq_domain_add_linear(struct device_node *of_node,
 					 unsigned int size,
-					 struct irq_domain_ops *ops,
+					 const struct irq_domain_ops *ops,
 					 void *host_data);
 struct irq_domain *irq_domain_add_nomap(struct device_node *of_node,
-					 struct irq_domain_ops *ops,
+					 const struct irq_domain_ops *ops,
 					 void *host_data);
 struct irq_domain *irq_domain_add_tree(struct device_node *of_node,
-					 struct irq_domain_ops *ops,
+					 const struct irq_domain_ops *ops,
 					 void *host_data);
 
 extern struct irq_domain *irq_find_host(struct device_node *node);
@@ -138,7 +138,7 @@
 
 static inline struct irq_domain *irq_domain_add_legacy_isa(
 				struct device_node *of_node,
-				struct irq_domain_ops *ops,
+				const struct irq_domain_ops *ops,
 				void *host_data)
 {
 	return irq_domain_add_legacy(of_node, NUM_ISA_INTERRUPTS, 0, 0, ops,
@@ -162,7 +162,7 @@
 extern unsigned int irq_linear_revmap(struct irq_domain *host,
 				      irq_hw_number_t hwirq);
 
-extern struct irq_domain_ops irq_domain_simple_ops;
+extern const struct irq_domain_ops irq_domain_simple_ops;
 
 /* stock xlate functions */
 int irq_domain_xlate_onecell(struct irq_domain *d, struct device_node *ctrlr,