HSI: omap_ssi_port: Fix return value check in ssi_debug_add_port()

In case of error, the function debugfs_create_*() returns NULL
pointer not ERR_PTR() if debugfs is enabled. The IS_ERR() test
in the return value check should be replaced with NULL test.

Signed-off-by: Wei Yongjun <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/hsi/controllers/omap_ssi_port.c

···
 	struct hsi_port *port = to_hsi_port(omap_port->dev);
 
 	dir = debugfs_create_dir(dev_name(omap_port->dev), dir);
-	if (IS_ERR(dir))
-		return PTR_ERR(dir);
+	if (!dir)
+		return -ENOMEM;
 	omap_port->dir = dir;
 	debugfs_create_file("regs", S_IRUGO, dir, port, &ssi_port_regs_fops);
 	dir = debugfs_create_dir("sst", dir);
-	if (IS_ERR(dir))
-		return PTR_ERR(dir);
+	if (!dir)
+		return -ENOMEM;
 	debugfs_create_file("divisor", S_IRUGO | S_IWUSR, dir, port,
 			    &ssi_sst_div_fops);