USB: serial: ir-usb: Silence harmless uninitialized variable warning

The "actual_length" variable might be uninitialized on some failure
paths.  It's harmless but static analysis tools like Smatch complain
and at runtime the UBSan tool will likely complain as well.

Fixes: e7542bc3 ("USB: serial: ir-usb: make set_termios synchronous")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Johan Hovold <johan@kernel.org>