dt-bindings: reset: Add binding constants for NPCM7xx reset controller

Add device tree binding constants for Nuvoton BMC NPCM7xx
reset controller.

Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>