gpio: ep93xx: Use for_each_set_bit() in IRQ handler

	struct gpio_chip *gc = irq_desc_get_handler_data(desc);

	struct ep93xx_gpio *epg = gpiochip_get_data(gc);

	struct irq_chip *irqchip = irq_desc_get_chip(desc);

	unsigned char status;

	int i;

	unsigned long stat;

	int offset;

	chained_irq_enter(irqchip, desc);

	status = readb(epg->base + EP93XX_GPIO_A_INT_STATUS);

	for (i = 0; i < 8; i++) {

		if (status & (1 << i)) {

			int gpio_irq = gpio_to_irq(0) + i;

	stat = readb(epg->base + EP93XX_GPIO_A_INT_STATUS);

	for_each_set_bit(offset, &stat, 8) {

		int gpio_irq = gpio_to_irq(0) + offset;

		generic_handle_irq(gpio_irq);

	}

	}

	status = readb(epg->base + EP93XX_GPIO_B_INT_STATUS);

	for (i = 0; i < 8; i++) {

		if (status & (1 << i)) {

			int gpio_irq = gpio_to_irq(8) + i;

	stat = readb(epg->base + EP93XX_GPIO_B_INT_STATUS);

	for_each_set_bit(offset, &stat, 8) {

		int gpio_irq = gpio_to_irq(8) + offset;

		generic_handle_irq(gpio_irq);

	}

	}

	chained_irq_exit(irqchip, desc);

}