sunxi: Rename Sinovoip BPI M2 Plus to Bananapi M2 Plus H3

The brand Sinovoip is used for Sinovoip's original VOIP products, while
the Bananapi brand is for the single board computers they produce. This
has been verified by Bananapi. Rename the board from "Sinovoip BPI M2
Plus" to "Bananapi M2 Plus". For the defconfig file, all lowercase is
used.

To support the H5 variant of this board, the "H3" suffix is added to
the defconfig name.

Also add myself as one of the board maintainers.

As the device tree files were already correctly named, they do not
require any changes.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
[jagan: removed unneeded message from commit body]
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>