mfd: tps65086: Constify struct regmap_irq_chip

`tps65086_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/tps65086.c

···
 	REGMAP_IRQ_REG(TPS65086_IRQ_FAULT, 0, TPS65086_IRQ_FAULT_MASK),
 };
 
-static struct regmap_irq_chip tps65086_irq_chip = {
+static const struct regmap_irq_chip tps65086_irq_chip = {
 	.name = "tps65086",
 	.status_base = TPS65086_IRQ,
 	.mask_base = TPS65086_IRQ_MASK,