gpio: sim: initialize a managed pointer when declaring it

Variables managed with __free() should typically be initialized where
they are declared so that the __free() callback is paired with its
counterpart resource allocator. Fix the second instance of using
__free() in gpio-sim to follow this pattern.

Fixes: 3faf89f2 ("gpio: sim: simplify code with cleanup helpers")
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

drivers/gpio/gpio-sim.c

@@ -1485,10 +1485,10 @@ static const struct config_item_type gpio_sim_device_config_group_type = {
 static struct config_group *
 gpio_sim_config_make_device_group(struct config_group *group, const char *name)
 {
-	struct gpio_sim_device *dev __free(kfree) = NULL;
 	int id;
 
-	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	struct gpio_sim_device *dev __free(kfree) = kzalloc(sizeof(*dev),
+							    GFP_KERNEL);
 	if (!dev)
 		return ERR_PTR(-ENOMEM);