arm64: dts: amlogic: add fbx8am board

The fbx8am boards are based on the Amlogic Meson G12A S905X2 SoC,
and the SEI510 board design.

Signed-off-by: Pierre-Hugues Husson <phhusson@freebox.fr>
Signed-off-by: Marc Gonzalez <mgonzalez@freebox.fr>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/59ca7d9a-a8dd-4062-852e-18b80ace6d7e@freebox.fr


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