i8k: Add support for Dell Latitude E6440

Dell Latitude E6440 needs same settings as E6540.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>