dt-bindings: arm: amlogic: add odroid-c4 bindings

Add the board bindings for the Hardkernel Odroid-C4 single board computer.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200506080702.6645-2-narmstrong@baylibre.com