sunxi: Add Libre Computer Board ALL-H3-CC H2+ ver.

This patch adds a device tree file for the H2+ version of the Libre
Computer Board ALL-H3-CC. It is the same board first introduced in
commit afe27544

 ("sunxi: Add support for Libre Computer Board
ALL-H3-CC H3 ver."), with the H3 SoC replaced with the H2+ SoC, and
has only two 2Gb DDR3 chips instead of four.

The device tree utilizes the common board design file for ALL-H3-CC,
providing just the model strings and SoC specifics.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>