gpio: generic: clamp retured value to [0,1]

The generic GPIO would return 0 for low generic GPIO, and
something != 0 for high GPIO. Let's make this sane by clamping
the returned value to [0,1].

Reported-by: Evgeny Boger <boger@contactless.ru>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-generic.c

@@ -139,7 +139,7 @@ static int bgpio_get(struct gpio_chip *gc, unsigned int gpio)
 {
 	struct bgpio_chip *bgc = to_bgpio_chip(gc);
 
-	return bgc->read_reg(bgc->reg_dat) & bgc->pin2mask(bgc, gpio);
+	return !!(bgc->read_reg(bgc->reg_dat) & bgc->pin2mask(bgc, gpio));
 }
 
 static void bgpio_set(struct gpio_chip *gc, unsigned int gpio, int val)