sunxi: Sync Bananapi M2+ device tree from Linux v5.0-rc1

As of commit aa8fee415f46 ("ARM: dts: sun8i: h3: Split out
non-SoC-specific parts of Bananapi M2 Plus") in the Linux kernel, the
device tree for the Bananapi M2+ has been split into a common dtsi file,
and an SoC-specific board device tree file that includes both the shared
dtsi file and the soc dtsi file. This was done to support both the H3
and H5 variants of the same board. This is similar to what was done for
the Libre Computer ALL-H3-CC in U-boot commit d7b17f1c

 ("sunxi: Split
out common board design for ALL-H3-CC device tree").

The newly split files are directly synced from Linux tag v5.0-rc1.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Jagan Teki <jagan@openedev.com>