usb: fix integer as NULL pointer warnings found by sparse

drivers/usb/host/ohci-sm501.c:93:24: warning: Using plain integer as NULL pointer
drivers/usb/gadget/amd5536udc.c:3254:9: warning: Using plain integer as NULL pointer
drivers/usb/gadget/amd5536udc.c:3267:9: warning: Using plain integer as NULL pointer
drivers/usb/gadget/amd5536udc.c:3277:9: warning: Using plain integer as NULL pointer
drivers/usb/gadget/amd5536udc.c:3285:9: warning: Using plain integer as NULL pointer
drivers/usb/gadget/amd5536udc.c:3293:9: warning: Using plain integer as NULL pointer

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/gadget/amd5536udc.c b/drivers/usb/gadget/amd5536udc.c
index ce337cb..f261d2a 100644
--- a/drivers/usb/gadget/amd5536udc.c
+++ b/drivers/usb/gadget/amd5536udc.c
@@ -3251,7 +3251,7 @@
 	/* pci setup */
 	if (pci_enable_device(pdev) < 0) {
 		kfree(dev);
-		dev = 0;
+		dev = NULL;
 		retval = -ENODEV;
 		goto finished;
 	}
@@ -3264,7 +3264,7 @@
 	if (!request_mem_region(resource, len, name)) {
 		dev_dbg(&pdev->dev, "pci device used already\n");
 		kfree(dev);
-		dev = 0;
+		dev = NULL;
 		retval = -EBUSY;
 		goto finished;
 	}
@@ -3274,7 +3274,7 @@
 	if (dev->virt_addr == NULL) {
 		dev_dbg(&pdev->dev, "start address cannot be mapped\n");
 		kfree(dev);
-		dev = 0;
+		dev = NULL;
 		retval = -EFAULT;
 		goto finished;
 	}
@@ -3282,7 +3282,7 @@
 	if (!pdev->irq) {
 		dev_err(&dev->pdev->dev, "irq not set\n");
 		kfree(dev);
-		dev = 0;
+		dev = NULL;
 		retval = -ENODEV;
 		goto finished;
 	}
@@ -3290,7 +3290,7 @@
 	if (request_irq(pdev->irq, udc_irq, IRQF_SHARED, name, dev) != 0) {
 		dev_dbg(&dev->pdev->dev, "request_irq(%d) fail\n", pdev->irq);
 		kfree(dev);
-		dev = 0;
+		dev = NULL;
 		retval = -EBUSY;
 		goto finished;
 	}