gpio: gpio-vf610: do not touch other bits when set the target bit

For gpio controller contain register PDDR, when set one target bit,
current logic will clear all other bits, this is wrong. Use operator
'|=' to fix it.

Fixes: 659d8a62 ("gpio: vf610: add imx7ulp support")
Reviewed-by: NPeng Fan <peng.fan@nxp.com>
Signed-off-by: NHaibo Chen <haibo.chen@nxp.com>
Signed-off-by: NBartosz Golaszewski <brgl@bgdev.pl>

drivers/gpio/gpio-vf610.c

@@ -125,9 +125,13 @@ static int vf610_gpio_direction_output(struct gpio_chip *chip, unsigned gpio,
 {
 	struct vf610_gpio_port *port = gpiochip_get_data(chip);
 	unsigned long mask = BIT(gpio);
+	u32 val;
 
-	if (port->sdata && port->sdata->have_paddr)
-		vf610_gpio_writel(mask, port->gpio_base + GPIO_PDDR);
+	if (port->sdata && port->sdata->have_paddr) {
+		val = vf610_gpio_readl(port->gpio_base + GPIO_PDDR);
+		val |= mask;
+		vf610_gpio_writel(val, port->gpio_base + GPIO_PDDR);
+	}
 
 	vf610_gpio_set(chip, gpio, value);