USB: cdc-acm: use negation for NULL checks

Use negation consistently throughout the driver for NULL checks.
Acked-by: NOliver Neukum <oneukum@suse.com>
Signed-off-by: NJohan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210322155318.9837-7-johan@kernel.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/cdc-acm.c

@@ -1336,7 +1336,7 @@ static int acm_probe(struct usb_interface *intf,
 	dev_dbg(&intf->dev, "interfaces are valid\n");
 
 	acm = kzalloc(sizeof(struct acm), GFP_KERNEL);
-	if (acm == NULL)
+	if (!acm)
 		return -ENOMEM;
 
 	tty_port_init(&acm->port);
@@ -1429,7 +1429,7 @@ static int acm_probe(struct usb_interface *intf,
 		struct acm_wb *snd = &(acm->wb[i]);
 
 		snd->urb = usb_alloc_urb(0, GFP_KERNEL);
-		if (snd->urb == NULL)
+		if (!snd->urb)
 			goto err_free_write_urbs;
 
 		if (usb_endpoint_xfer_int(epwrite))