dt-bindings: mtd: nand-chip: Reference mtd.yaml

A NAND chip is an MTD device. mtd.yaml already defines many useful and
relevant properties, let's reference this file here to get access to
these additional property definitions.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/linux-mtd/20221114090315.848208-4-miquel.raynal@bootlin.com