leds: verify vendor and change license in mlxcpld driver

Verify that vendor is Mellanox as the first step of initialization.
If it is not - return ENODEV.
Change module license from "GPL v2" to "Dual BSD/GPL".

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>