arm64: dts: amlogic: meson-g12b-bananapi-cm4: add support for MNT Reform2 with CM4 adaper

This adds a basic devicetree for the MNT Reform2 DIY laptop when using a
CM4 adapter and a BPI-CM4 module.

Co-developed-by: Lukas F. Hartmann <lukas@mntre.com>
Link: https://lore.kernel.org/r/20240403-amlogic-v6-4-upstream-dsi-ccf-vim3-v12-7-99ecdfdc87fc@linaro.org


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>