mfd: twl6040: Constify struct regmap_irq_chip

`twl6040_irq_chip` is not modified and can be declared as const to
move its data to a read-only section.
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20240704-mfd-const-regmap_config-v2-21-0c8785b1331d@gmail.comSigned-off-by: Lee Jones <lee@kernel.org>

drivers/mfd/twl6040.c

@@ -620,7 +620,7 @@ static const struct regmap_irq twl6040_irqs[] = {
 	{ .reg_offset = 0, .mask = TWL6040_READYINT, },
 };
 
-static struct regmap_irq_chip twl6040_irq_chip = {
+static const struct regmap_irq_chip twl6040_irq_chip = {
 	.name = "twl6040",
 	.irqs = twl6040_irqs,
 	.num_irqs = ARRAY_SIZE(twl6040_irqs),