[U-Boot] uboot support to Allwinner bananapi zero

[Jun Nie]

Hi Icenowy & Jagan,

I see bananapi zero patch was posted and discussed in [1], but without
further follow up. Maybe we can decide which name is more maintainable
first, bananapi-*, Bananapi-* or Sinovoip_BPI_*. And add all new
boards with following the rule. Which one do you prefer?

If possible, we can create symbol link or just rename files later as
it may cause issue for end user.

[1] https://patchwork.ozlabs.org/patch/832937/
[2] https://patchwork.kernel.org/patch/9753547/

Jun