mfd: hi655x-pmic: Fixup issue with un-acked interrupts

While trying to get the powerkey to function, I found when
pressing the key, I would get infinitely repeating interrupts.

After digging around a bit, it seems we didn't set the ack_base
value for the regmap irqchip logic, so nothing was acking the
interrupt.

This patch adds the ack_base, which seems to make things work.
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/hi655x-pmic.c

@@ -45,6 +45,7 @@ static const struct regmap_irq_chip hi655x_irq_chip = {
 	.num_regs = 1,
 	.num_irqs = ARRAY_SIZE(hi655x_irqs),
 	.status_base = HI655X_IRQ_STAT_BASE,
+	.ack_base = HI655X_IRQ_STAT_BASE,
 	.mask_base = HI655X_IRQ_MASK_BASE,
 };