dt-bindings: mtd: ingenic: Add compatible strings for JZ4740 and JZ4725B

Add compatible strings to probe the jz4780-nand and jz4780-bch drivers
from devicetree on the JZ4725B and JZ4740 SoCs from Ingenic.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>