dt-bindings: mtd: ti,elm: Convert to yaml

Convert elm.txt to ti,elm.yaml.

hwmod framework use is deprecated for new platforms
so mark it so.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220326080726.30372-2-rogerq@kernel.org