ACPI / property: Extend device_get_next_child_node() to data-only nodes

Make device_get_next_child_node() work with ACPI data-only subnodes
introduced previously.

Namely, replace acpi_get_next_child() with acpi_get_next_subnode()
that can handle (and return) child device objects as well as child
data-only subnodes of the given device and modify the ACPI part
of the GPIO subsystem to handle data-only subnodes returned by it.

To that end, introduce acpi_node_get_gpiod() taking a struct
fwnode_handle pointer as the first argument.  That argument may
point to an ACPI device object as well as to a data-only subnode
and the function should do the right thing (ie. look for the matching
GPIO descriptor correctly) in either case.

Next, modify fwnode_get_named_gpiod() to use acpi_node_get_gpiod()
instead of acpi_get_gpiod_by_index() which automatically causes
devm_get_gpiod_from_child() to work with ACPI data-only subnodes
that may be returned by device_get_next_child_node() which in turn
is required by the users of that function (the gpio_keys_polled
and gpio-leds drivers).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f43e808..7d61b50 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2083,11 +2083,10 @@
 						&flags);
 		if (!IS_ERR(desc))
 			active_low = flags & OF_GPIO_ACTIVE_LOW;
-	} else if (is_acpi_device_node(fwnode)) {
+	} else if (is_acpi_node(fwnode)) {
 		struct acpi_gpio_info info;
 
-		desc = acpi_get_gpiod_by_index(to_acpi_device_node(fwnode),
-					       propname, 0, &info);
+		desc = acpi_node_get_gpiod(fwnode, propname, 0, &info);
 		if (!IS_ERR(desc))
 			active_low = info.active_low;
 	}