drivers: misc: add Renesas RA ELC driver

Add support for the Renesas RA Event Link Controller, including
driver sources, Kconfig, and Devicetree bindings.

Signed-off-by: Khanh Nguyen <khanh.nguyen.wz@bp.renesas.com>
Signed-off-by: Khoa Nguyen <khoa.nguyen.xh@renesas.com>