Add RS232 support for Edgeble Neu6B NCM IO board.
Signed-off-by: Jagan Teki <jagan@edgeble.ai>
Link: https://lore.kernel.org/r/20230713143941.1756849-7-jagan@edgeble.aiSigned-off-by: Heiko Stuebner <heiko@sntech.de>