Net, USB, Option, hso: Do not dereference NULL pointer

In drivers/net/usb/hso.c::hso_create_bulk_serial_device() we have this
code:
...
	serial = kzalloc(sizeof(*serial), GFP_KERNEL);
	if (!serial)
		goto exit;
...
exit:
	hso_free_tiomget(serial);
...
hso_free_tiomget() directly dereferences its argument, which in the
example above is a NULL pointer, ouch.
I could just add a 'if (serial)' test at the 'exit' label, but since most
freeing functions in the kernel accept NULL pointers (and it seems like
this was also assumed here) I opted to instead change 'hso_free_tiomget()'
so that it is safe to call it with a NULL argument. I also modified the
function to get rid of a pointles conditional before the call to
'usb_free_urb()' since that function already tests for NULL itself -
besides fixing the NULL deref this change also buys us a few bytes in
size.
Before:
$ size drivers/net/usb/hso.o
   text    data     bss     dec     hex filename
  32200     592    9960   42752    a700 drivers/net/usb/hso.o
After:
$ size drivers/net/usb/hso.o
   text    data     bss     dec     hex filename
  32196     592    9960   42748    a6fc drivers/net/usb/hso.o
Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/hso.c

@@ -2628,15 +2628,15 @@ static struct hso_device *hso_create_net_device(struct usb_interface *interface,
 
 static void hso_free_tiomget(struct hso_serial *serial)
 {
-	struct hso_tiocmget *tiocmget = serial->tiocmget;
+	struct hso_tiocmget *tiocmget;
+	if (!serial)
+		return;
+	tiocmget = serial->tiocmget;
 	if (tiocmget) {
-		if (tiocmget->urb) {
 		usb_free_urb(tiocmget->urb);
 		tiocmget->urb = NULL;
-		}
 		serial->tiocmget = NULL;
 		kfree(tiocmget);
-
 	}
 }