dt-bindings: arm: amlogic: add MeCool KII/KIII Pro bindings

Add the board bindings for the MeCool (Videostrong Technology Co., Ltd)
KII-Pro (S905D) and KIII-Pro (S912) devices.

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20210402064521.30579-2-christianshewitt@gmail.com