oradax: Fix return value check in dax_attach()

In case of error, the function class_create() returns ERR_PTR() and
never returns NULL. The NULL test in the return value check should be
replaced with IS_ERR().

Fixes: dd027328 ("sparc64: Oracle DAX driver")
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/sbus/char/oradax.c

@@ -336,9 +336,9 @@ static int __init dax_attach(void)
 	}
 
 	cl = class_create(THIS_MODULE, DAX_NAME);
-	if (cl == NULL) {
+	if (IS_ERR(cl)) {
 		dax_err("class_create failed");
-		ret = -ENXIO;
+		ret = PTR_ERR(cl);
 		goto class_error;
 	}