powerpc: simple_gpio: Be sure to clamp return value

As we want gpio_chip .get() calls to be able to return negative
error codes and propagate to drivers, we need to go over all
drivers and make sure their return values are clamped to [0,1].
We do this by using the ret = !!(val) design pattern.

Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Anatolij Gustschin <agust@denx.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/powerpc/sysdev/simple_gpio.c

@@ -46,7 +46,7 @@ static int u8_gpio_get(struct gpio_chip *gc, unsigned int gpio)
 {
 	struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
 
-	return in_8(mm_gc->regs) & u8_pin2mask(gpio);
+	return !!(in_8(mm_gc->regs) & u8_pin2mask(gpio));
 }
 
 static void u8_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)