arm64: dts: amlogic: add libretech cottonwood support

arm64: dts: amlogic: add libretech cottonwood support

Add support for the Libretech cottonwood board family.
These 2 boards are based on the same PCB, with an RPi B form factor.

The "Alta" board uses an a311d while the "Solitude" variant uses an s905d3.

Co-developed-by: Da Xue <da.xue@libretech.co>
Signed-off-by: Da Xue <da.xue@libretech.co>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20231006103500.2015183-3-jbrunet@baylibre.com
[narmstrong: squashed blue/green led inversion fix]
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>