USB: fix dereference in drivers/usb/misc/adutux.c

in two of the error cases, dev is still NULL,
and we dereference it. Spotted by coverity (cid#1428, 1429)

Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/misc/adutux.c

@@ -370,7 +370,8 @@ static int adu_release(struct inode *inode, struct file *file)
 	retval = adu_release_internal(dev);
 
 exit:
-	up(&dev->sem);
+	if (dev)
+		up(&dev->sem);
 	dbg(2," %s : leave, return value %d", __FUNCTION__, retval);
 	return retval;
 }