gpio: lynxpoint: Move hardware initialization to callback

The driver wants to initialize related registers before IRQ chip will be added.
That's why move it to a corresponding callback. It also fixes the NULL pointer
dereference.

Fixes: 7b1e8894 ("gpio: lynxpoint: Pass irqchip when adding gpiochip")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-lynxpoint.c

@@ -294,8 +294,9 @@ static struct irq_chip lp_irqchip = {
 	.flags = IRQCHIP_SKIP_SET_WAKE,
 };
 
-static void lp_gpio_irq_init_hw(struct lp_gpio *lg)
+static int lp_gpio_irq_init_hw(struct gpio_chip *chip)
 {
+	struct lp_gpio *lg = gpiochip_get_data(chip);
 	unsigned long reg;
 	unsigned base;
 
@@ -307,6 +308,8 @@ static void lp_gpio_irq_init_hw(struct lp_gpio *lg)
 		reg = lp_gpio_reg(&lg->chip, base, LP_INT_STAT);
 		outl(0xffffffff, reg);
 	}
+
+	return 0;
 }
 
 static int lp_gpio_probe(struct platform_device *pdev)
@@ -364,6 +367,7 @@ static int lp_gpio_probe(struct platform_device *pdev)
 
 		girq = &gc->irq;
 		girq->chip = &lp_irqchip;
+		girq->init_hw = lp_gpio_irq_init_hw;
 		girq->parent_handler = lp_gpio_irq_handler;
 		girq->num_parents = 1;
 		girq->parents = devm_kcalloc(&pdev->dev, girq->num_parents,
@@ -374,8 +378,6 @@ static int lp_gpio_probe(struct platform_device *pdev)
 		girq->parents[0] = (unsigned)irq_rc->start;
 		girq->default_type = IRQ_TYPE_NONE;
 		girq->handler = handle_simple_irq;
-
-		lp_gpio_irq_init_hw(lg);
 	}
 
 	ret = devm_gpiochip_add_data(dev, gc, lg);