USB: hcd.c: quiet NULL pointer sparse noise

Quiet the following sparse noise:

  warning: Using plain integer as NULL pointer
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/hcd.c

@@ -1607,7 +1607,7 @@ int usb_hcd_check_bandwidth(struct usb_device *udev,
 {
 	int num_intfs, i, j;
 	struct usb_interface_cache *intf_cache;
-	struct usb_host_interface *alt = 0;
+	struct usb_host_interface *alt = NULL;
 	int ret = 0;
 	struct usb_hcd *hcd;
 	struct usb_host_endpoint *ep;