mcb: request_mem_region() returns NULL on error

The code here is checking for IS_ERR() when request_mem_region() only
returns NULL on error and never an ERR_PTR.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/mcb/mcb-pci.c b/drivers/mcb/mcb-pci.c
index 0af7361..de36237 100644
--- a/drivers/mcb/mcb-pci.c
+++ b/drivers/mcb/mcb-pci.c
@@ -56,9 +56,9 @@
 
 	res = request_mem_region(priv->mapbase, CHAM_HEADER_SIZE,
 				 KBUILD_MODNAME);
-	if (IS_ERR(res)) {
+	if (!res) {
 		dev_err(&pdev->dev, "Failed to request PCI memory\n");
-		ret = PTR_ERR(res);
+		ret = -EBUSY;
 		goto out_disable;
 	}