dt-bindings: trivial-devices: Add Delta DPS920AB

Add trivial device entry for Delta DPS920AB PSU.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Link: https://lore.kernel.org/r/20210607103431.2039073-2-robert.marko@sartura.hr


Signed-off-by: Guenter Roeck <linux@roeck-us.net>