gpio: stp-xway: Implement get callback

Add an implementation to get the current GPIO state.

The callback is used by the leds-gpio driver for example, in case the
current LED/GPIO state should be kept during driver load.

Signed-off-by: Mathias Kresin <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/gpio/gpio-stp-xway.c

···
 };
 
 /**
+ * xway_stp_get() - gpio_chip->get - get gpios.
+ * @gc:     Pointer to gpio_chip device structure.
+ * @gpio:   GPIO signal number.
+ *
+ * Gets the shadow value.
+ */
+static int xway_stp_get(struct gpio_chip *gc, unsigned int gpio)
+{
+	struct xway_stp *chip = gpiochip_get_data(gc);
+
+	return (xway_stp_r32(chip->virt, XWAY_STP_CPU0) & BIT(gpio));
+}
+
+/**
  * xway_stp_set() - gpio_chip->set - set gpios.
  * @gc:     Pointer to gpio_chip device structure.
  * @gpio:   GPIO signal number.
···
 	chip->gc.parent = &pdev->dev;
 	chip->gc.label = "stp-xway";
 	chip->gc.direction_output = xway_stp_dir_out;
+	chip->gc.get = xway_stp_get;
 	chip->gc.set = xway_stp_set;
 	chip->gc.request = xway_stp_request;
 	chip->gc.base = -1;