[PATCH v1] sync doc/README.socfpga with new info

[Sune Brian]

> Right, so the first thing to do is migrate doc/README.socfpga to rST
> probably as doc/board/socfpga/index.rst (and include that in

Actually Tom, If you really need this documentation.
Thing will become very trouble and even difficult.
FPGA + SoC is a huge kind of SoC. Brand
involved Altera, Xilinx, Microsemi, Lattice.
All these big brand have FPSoC, and to document
all these is almost impossible. There are too many
brand and board.

Meantime, they all feel like they are not willing to
merge to mainstream U-Boot. Rather than pulling
from main stream and host its own vendor variant.

My goal is just trying to make  Altera GEN5 SoC
works on mainstream, as it is forgotten long long
time. And even some patch from Altera staff, breaks
the build and result in an unbootable build.

Brian