Switch the DT binding to a YAML schema to enable the DT validation.

There was also an incorrect reference to dma-names being "rxtx" where
the driver and existing device trees actually use dma-names = "data" so
this is corrected in the conversion.
Signed-off-by: Vadym Kochan <vadym.kochan@plvision.eu>
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230619040742.1108172-2-chris.packham@alliedtelesis.co.nz