U-Boot: Add SOPINE Baseboard build

This build is compatible with PINE A64-LTS.

[dezgeg changed the original device tree patch to v4 of the patch series
"sunxi: sync H3, H5, A64 DTs from mainline Linux" submitted to the
upstream mailing list by Andre Przywara. Also install the
u-boot-sunxi-with-spl.bin binary similar to 32-bit boards
since it's now being built by the upstream build system.]