mfd: tps65218: Constify struct regmap_irq_chip

`tps65218_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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/tps65218.c

···
 	},
 };
 
-static struct regmap_irq_chip tps65218_irq_chip = {
+static const struct regmap_irq_chip tps65218_irq_chip = {
 	.name = "tps65218",
 	.irqs = tps65218_irqs,
 	.num_irqs = ARRAY_SIZE(tps65218_irqs),