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

The Odroid-C4 is the Odroid-C2 successor with same form factor, but using
a modern Amlogic S905X3 (SM1) SoC and 4x USB3 ports.
Signed-off-by: Dongjin Kim <tobetter@gmail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20200506080702.6645-3-narmstrong@baylibre.com