sunxi: Add Bananapi M2+ H5 board

As the H5 is pin compatible with the H3, vendors tend to upgrade their
existing H3 products with an H5 SoC swap. This is the case with the
Bananapi M2+ H5.

Add the following to support it:

  - device tree file: synced from Linux v5.0-rc1,
  - defconfig: copy of bananapi_m2_plus_h3_defconfig with only SoC
	       family and default device tree file name changed
  - MAINTAINERS entry

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