arm: boards: phytec-som-am335x: Remove 1GB RAM type
This machine was a prototype and was never shipped to customers.
Since it has no dependencies to any image, it can be removed.
Signed-off-by: Daniel Schultz <d.schultz@phytec.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>