regmap: kunit: Fix an NULL vs IS_ERR() check

The kunit_device_register() function returns error pointers, not NULL.
Passing an error pointer to get_device() will lead to an Oops.  Also
get_device() returns the same device you passed to it.  Fix it!  ;)

Fixes: 7b7982f ("regmap: kunit: Create a struct device for the regmap")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/b32e80cf-b385-40cd-b8ec-77ec73e07530@moroto.mountain
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Dan Carpenter

drivers/base/regmap/regmap-kunit.c

@@ -1925,10 +1925,10 @@ static int regmap_test_init(struct kunit *test)
 	test->priv = priv;
 
 	dev = kunit_device_register(test, "regmap_test");
-	priv->dev = get_device(dev);
-	if (!priv->dev)
-		return -ENODEV;
+	if (IS_ERR(dev))
+		return PTR_ERR(dev);
 
+	priv->dev = get_device(dev);
 	dev_set_drvdata(dev, test);
 
 	return 0;