gpiolib: Force wm831x GPIOs into GPIO mode when requested

This is the chip default but it's possible the bootloader or OTP
will have been configured to a different mode (eg, to provide
feedback during startup).

Signed-off-by: Mark Brown <[e-mail]>
Signed-off-by: Samuel Ortiz <[e-mail]>

drivers/gpio/wm831x-gpio.c

···
 		val |= WM831X_GPN_TRI;
 
 	return wm831x_set_bits(wm831x, WM831X_GPIO1_CONTROL + offset,
-			       WM831X_GPN_DIR | WM831X_GPN_TRI, val);
+			       WM831X_GPN_DIR | WM831X_GPN_TRI |
+			       WM831X_GPN_FN_MASK, val);
 }
 
 static int wm831x_gpio_get(struct gpio_chip *chip, unsigned offset)
···
 		val |= WM831X_GPN_TRI;
 
 	ret = wm831x_set_bits(wm831x, WM831X_GPIO1_CONTROL + offset,
-			      WM831X_GPN_DIR | WM831X_GPN_TRI, val);
+			      WM831X_GPN_DIR | WM831X_GPN_TRI |
+			      WM831X_GPN_FN_MASK, val);
 	if (ret < 0)
 		return ret;