Edgeble Neu6a and Neu6b are compatible with common IO board.

So, maintain the IO board in rk3588-edgeble-neu6a-io.dtsi.
Signed-off-by: Jagan Teki <jagan@edgeble.ai>
Link: https://lore.kernel.org/r/20231125190522.87607-4-jagan@edgeble.aiSigned-off-by: Heiko Stuebner <heiko@sntech.de>