regmap: Constify regmap_irq_chip

We should never be modifying it and it lets drivers declare it const.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 26136b5..f9b624c 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -268,7 +268,7 @@
 struct regmap_irq_chip_data;
 
 int regmap_add_irq_chip(struct regmap *map, int irq, int irq_flags,
-			int irq_base, struct regmap_irq_chip *chip,
+			int irq_base, const struct regmap_irq_chip *chip,
 			struct regmap_irq_chip_data **data);
 void regmap_del_irq_chip(int irq, struct regmap_irq_chip_data *data);
 int regmap_irq_chip_get_base(struct regmap_irq_chip_data *data);