gpiolib: Preserve desc->flags when setting state

desc->flags may already have values set by of_gpiochip_add() so make
sure that this isn't undone when setting the initial direction.

Cc: stable@vger.kernel.org
Fixes: 3edfb7b ("gpiolib: Show correct direction from the beginning")
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20190707203558.10993-1-chris.packham@alliedtelesis.co.nz
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -1394,12 +1394,17 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
 	for (i = 0; i < chip->ngpio; i++) {
 		struct gpio_desc *desc = &gdev->descs[i];
 
-		if (chip->get_direction && gpiochip_line_is_valid(chip, i))
-			desc->flags = !chip->get_direction(chip, i) ?
-					(1 << FLAG_IS_OUT) : 0;
-		else
-			desc->flags = !chip->direction_input ?
-					(1 << FLAG_IS_OUT) : 0;
+		if (chip->get_direction && gpiochip_line_is_valid(chip, i)) {
+			if (!chip->get_direction(chip, i))
+				set_bit(FLAG_IS_OUT, &desc->flags);
+			else
+				clear_bit(FLAG_IS_OUT, &desc->flags);
+		} else {
+			if (!chip->direction_input)
+				set_bit(FLAG_IS_OUT, &desc->flags);
+			else
+				clear_bit(FLAG_IS_OUT, &desc->flags);
+		}
 	}
 
 	acpi_gpiochip_add(chip);