dt-bindings: mtd: Convert ti, am654-hbmc.txt to YAML schema

Convert ti,am654-hbmc.txt to YAML schema for better checks and
validations of DT.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>