ntb: hw: amd: Fix debugfs_create_dir error checking

The debugfs_create_dir function returns ERR_PTR in case of error, and the
only correct way to check if an error occurred is 'IS_ERR' inline function.
This patch will replace the null-comparison with IS_ERR.
Signed-off-by: Anup Sharma <anupnewsmail@gmail.com>
Suggested-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

drivers/ntb/hw/amd/ntb_hw_amd.c

@@ -941,7 +941,7 @@ static void ndev_init_debugfs(struct amd_ntb_dev *ndev)
 		ndev->debugfs_dir =
 			debugfs_create_dir(pci_name(ndev->ntb.pdev),
 					   debugfs_dir);
-		if (!ndev->debugfs_dir)
+		if (IS_ERR(ndev->debugfs_dir))
 			ndev->debugfs_info = NULL;
 		else
 			ndev->debugfs_info =