base: core: Remove WARN_ON from link dependencies check

In some cases the link between between customer and supplier
already exist, for example when a device use its parent as a supplier.
Do not warn about already existing dependencies because device_link_add()
takes care of this case.

Link: http://lkml.kernel.org/r/20180709111753eucas1p1f32e66fb2f7ea3216097cd72a132355d~-rzycA5Rg0378203782eucas1p1C@eucas1p1.samsung.com

Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/core.c

@@ -105,15 +105,15 @@ static int device_is_dependent(struct device *dev, void *target)
 	struct device_link *link;
 	int ret;
 
-	if (WARN_ON(dev == target))
+	if (dev == target)
 		return 1;
 
 	ret = device_for_each_child(dev, target, device_is_dependent);
 	if (ret)
 		return ret;
 
 	list_for_each_entry(link, &dev->links.consumers, s_node) {
-		if (WARN_ON(link->consumer == target))
+		if (link->consumer == target)
 			return 1;
 
 		ret = device_is_dependent(link->consumer, target);