When a threaded irq handler is chained attached to one of the gpio
pins when configure for level irq the altera_gpio_irq_leveL_high_handler
does not mask the interrupt while being handled by the chained irq.
This resulting in the threaded irq not getting enough cycles to complete
quickly enough before the irq was disabled as faulty. handle_level_irq
should be used in this situation instead of handle_simple_irq.

In gpiochip_irqchip_add set default handler to handle_bad_irq as
per Documentation/gpio/driver.txt. Then set the correct handler in
the set_type callback.

Signed-off-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>