gpio: sandbox: Add GPIOD_IS_AF for gpio configured in alternate function

This allows to test if a pin's label if displayed using gpio_get_status()
when this pin is configured in alternate function.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/drivers/gpio/sandbox.c b/drivers/gpio/sandbox.c
index 106b2a7..305f9a6 100644
--- a/drivers/gpio/sandbox.c
+++ b/drivers/gpio/sandbox.c
@@ -196,6 +196,8 @@
 		return GPIOF_OUTPUT;
 	if (get_gpio_flag(dev, offset, GPIOD_IS_IN))
 		return GPIOF_INPUT;
+	if (get_gpio_flag(dev, offset, GPIOD_IS_AF))
+		return GPIOF_FUNC;
 
 	return GPIOF_INPUT; /*GPIO is not configurated */
 }
@@ -219,6 +221,9 @@
 	if (args->args[1] & GPIO_OUT_ACTIVE)
 		desc->flags |= GPIOD_IS_OUT_ACTIVE;
 
+	if (args->args[1] & GPIO_AF)
+		desc->flags |= GPIOD_IS_AF;
+
 	return 0;
 }