USB: cdc-acm: fix invalid user-pointer check

Drop invalid user-pointer check from TIOCGSERIAL handler.

A NULL-pointer can be valid in user space and copy_to_user() takes care
of sanity checking.
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/cdc-acm.c

@@ -877,9 +877,6 @@ static int get_serial_info(struct acm *acm, struct serial_struct __user *info)
 {
 	struct serial_struct tmp;
 
-	if (!info)
-		return -EINVAL;
-
 	memset(&tmp, 0, sizeof(tmp));
 	tmp.flags = ASYNC_LOW_LATENCY;
 	tmp.xmit_fifo_size = acm->writesize;