dt-bindings: mtd: Add YAML schemas for the generic NAND options

The NAND chips in MTD have a bunch of generic options that are needed in a
device tree. Add a YAML schemas for those.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>