gpiolib: Respect error code of ->get_direction()

In case we try to lock GPIO pin as IRQ when something going wrong
we print a misleading message.

Correct this by checking an error code from ->get_direction() in
gpiochip_lock_as_irq() and printing a corresponding message.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -3262,6 +3262,12 @@ int gpiochip_lock_as_irq(struct gpio_chip *chip, unsigned int offset)
 	if (!chip->can_sleep && chip->get_direction) {
 		int dir = chip->get_direction(chip, offset);
 
+		if (dir < 0) {
+			chip_err(chip, "%s: cannot get GPIO direction\n",
+				 __func__);
+			return dir;
+		}
+
 		if (dir)
 			clear_bit(FLAG_IS_OUT, &desc->flags);
 		else