mfd: Constify regmap and irq configuration data

Constify in various drivers configuration data which is not modified:
 - regmap_irq_chip,
 - individual regmap_irq's in array,
 - regmap_config,
 - irq_domain_ops,

Signed-off-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/tps6586x.c b/drivers/mfd/tps6586x.c
index 8e1dbc4..e0a2583 100644
--- a/drivers/mfd/tps6586x.c
+++ b/drivers/mfd/tps6586x.c
@@ -311,7 +311,7 @@
 	return 0;
 }
 
-static struct irq_domain_ops tps6586x_domain_ops = {
+static const struct irq_domain_ops tps6586x_domain_ops = {
 	.map    = tps6586x_irq_map,
 	.xlate  = irq_domain_xlate_twocell,
 };