gpio: max732x: Fix irq-events handler

MAX732X clears all pending interrupts on I2C read (when interrupts
register is being read). Driver doesn't need to send any ACKs when
interrupt was handled. So replace handle_edge_irq() with
handle_simple_irq().

Using handle_edge_irq() (w/o .irq_ack callback set) may lead to NULL
pointer dereference in some cases. E.g. this was observed on
hibernation process:

Unable to handle kernel NULL pointer dereference at virtual address 0
Backtrace:
(handle_edge_irq) from (resend_irqs)
(resend_irqs) from (tasklet_action)
(tasklet_action) from (__do_softirq)
(__do_softirq) from (run_ksoftirqd)
(run_ksoftirqd) from (smpboot_thread_fn)
(smpboot_thread_fn) from (kthread)
(kthread) from (ret_from_fork)

Signed-off-by: Semen Protsenko <[e-mail]>
Reviewed-by: Grygorii Strashko <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/gpio/gpio-max732x.c

···
 		ret =  gpiochip_irqchip_add(&chip->gpio_chip,
 					    &max732x_irq_chip,
 					    irq_base,
-					    handle_edge_irq,
+					    handle_simple_irq,
 					    IRQ_TYPE_NONE);
 		if (ret) {
 			dev_err(&client->dev,