gpio: viperboard: 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: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpio-viperboard.c b/drivers/gpio/gpio-viperboard.c
index 26e7edb..7667e77 100644
--- a/drivers/gpio/gpio-viperboard.c
+++ b/drivers/gpio/gpio-viperboard.c
@@ -95,7 +95,7 @@
 
 	/* if io is set to output, just return the saved value */
 	if (gpio->gpioa_out & (1 << offset))
-		return gpio->gpioa_val & (1 << offset);
+		return !!(gpio->gpioa_val & (1 << offset));
 
 	mutex_lock(&vb->lock);