[PATCH] test_overflow: fix an IS_ERR() vs NULL bug

[Dan Carpenter]

root_device_register() returns error pointers, it never returns NULL.

Fixes: ca90800a91ba ("test_overflow: Add memory allocation overflow tests")
Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>

diff --git a/lib/test_overflow.c b/lib/test_overflow.c
index aecbbb217305..2278fe05a1b0 100644
--- a/lib/test_overflow.c
+++ b/lib/test_overflow.c
@@ -367,7 +367,7 @@ static int __init test_overflow_allocation(void)
 
        /* Create dummy device for devm_kmalloc()-family tests. */
        dev = root_device_register(device_name);
-       if (!dev) {
+       if (IS_ERR(dev)) {
                pr_warn("Cannot register test device\n");
                return 1;
        }