dt-bindings: arm: amlogic: add SEI Robotics SEI610 bindings

Add the compatible for the Amlogic SM1 Based SEI610 board.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>