pch_phub: fix sparse warning

sparse warns about using 0 as NULL pointer,

drivers/misc/pch_phub.c:702:44: warning: Using plain integer as NULL pointer
Signed-off-by: NDevendra Naga <develkernel412222@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/pch_phub.c

@@ -699,7 +699,7 @@ static int __devinit pch_phub_probe(struct pci_dev *pdev,
 	chip->pch_phub_base_address = pci_iomap(pdev, 1, 0);
 
 
-	if (chip->pch_phub_base_address == 0) {
+	if (chip->pch_phub_base_address == NULL) {
 		dev_err(&pdev->dev, "%s : pci_iomap FAILED", __func__);
 		ret = -ENOMEM;
 		goto err_pci_iomap;