gpio: fix aspeed_gpio unmask irq

The unmask function disables all interrupts in a bank when unmasking an
interrupt. Only disable the given interrupt.

Cc: stable@vger.kernel.org
Signed-off-by: Govert Overgaauw <govert.overgaauw@prodrive-technologies.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-aspeed.c

@@ -384,7 +384,7 @@ static void aspeed_gpio_irq_set_mask(struct irq_data *d, bool set)
 	if (set)
 		reg |= bit;
 	else
-		reg &= bit;
+		reg &= ~bit;
 	iowrite32(reg, addr);
 
 	spin_unlock_irqrestore(&gpio->lock, flags);