dt-bindings: omap: Add Seeed BeagleBone Green Eco

Document the seeed,am335x-bone-green-eco compatible string in the
appropriate place within the omap family binding file.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Reviewed-by: Andreas Kemnade <andreas@kemnade.info>
Tested-by: Judith Mendez <jm@ti.com>
Link: https://lore.kernel.org/r/20250620-bbg-v5-2-84f9b9a2e3a8@bootlin.com


Signed-off-by: Kevin Hilman <khilman@baylibre.com>