bonding: use IS_ERR instead of NULL check in bond_create_debugfs

Because debugfs_create_dir returns ERR_PTR, so IS_ERR should be used to
check whether the directory is successfully created.
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_debugfs.c

@@ -88,7 +88,7 @@ void __init bond_create_debugfs(void)
 {
 	bonding_debug_root = debugfs_create_dir("bonding", NULL);
 
-	if (!bonding_debug_root)
+	if (IS_ERR(bonding_debug_root))
 		pr_warn("Warning: Cannot create bonding directory in debugfs\n");
 }