gpio: rcar: Check for irq_set_irq_wake() failures

If an interrupt controller doesn't support wake-up configuration,
irq_set_irq_wake() returns an error code.  Then any subsequent call
trying to deconfigure wake-up will cause an imbalance, and a warning
will be printed:

    WARNING: CPU: 1 PID: 1341 at kernel/irq/manage.c:540 irq_set_irq_wake+0x9c/0xf8()
    Unbalanced IRQ 26 wake disable

To fix this, refrain from any further parent interrupt controller
(de)configuration if irq_set_irq_wake() failed.

Alternative fixes would be:
  - calling "gic_set_irqchip_flags(IRQCHIP_SKIP_SET_WAKE)" from the
    platform code,
  - setting "gic_chip.flags = IRQCHIP_SKIP_SET_WAKE" in the GIC driver
    code,
but these were withheld as the GIC hardware doesn't really support
wake-up interrupts.

Fixes: ab82fa7d ("gpio: rcar: Prevent module clock disable when wake-up is enabled")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-rcar.c

@@ -177,8 +177,17 @@ static int gpio_rcar_irq_set_wake(struct irq_data *d, unsigned int on)
 	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
 	struct gpio_rcar_priv *p = container_of(gc, struct gpio_rcar_priv,
 						gpio_chip);
-
-	irq_set_irq_wake(p->irq_parent, on);
+	int error;
+
+	if (p->irq_parent) {
+		error = irq_set_irq_wake(p->irq_parent, on);
+		if (error) {
+			dev_dbg(&p->pdev->dev,
+				"irq %u doesn't support irq_set_wake\n",
+				p->irq_parent);
+			p->irq_parent = 0;
+		}
+	}
 
 	if (!p->clk)
 		return 0;