kunit: Fix a NULL vs IS_ERR() bug

The kunit_device_register() function doesn't return NULL, it returns
error pointers.  Change the KUNIT_ASSERT_NOT_NULL() to check for
ERR_OR_NULL().

Fixes: d03c720 ("kunit: Add APIs for managing devices")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Rae Moar <rmoar@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Author: Dan Carpenter

lib/kunit/kunit-test.c

@@ -720,7 +720,7 @@ static void kunit_device_cleanup_test(struct kunit *test)
 	long action_was_run = 0;
 
 	test_device = kunit_device_register(test, "my_device");
-	KUNIT_ASSERT_NOT_NULL(test, test_device);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, test_device);
 
 	/* Add an action to verify cleanup. */
 	devm_add_action(test_device, test_dev_action, &action_was_run);