This PR adds support for the PINE64 StarPro64 64-bit RISC-V SBC,
based on ESWIN EIC7700X SoC. Most of the code was derived from NuttX
for Milk-V Duo S (SOPHGO SG2000). The modified code is explained here:
https://lupyuen.github.io/articles/starpro64#appendix-port-nuttx-to-starpro64
`platforms/risc-v/eic7700x/index.rst`:
Added StarPro64 to EIC7700X SoC
`platforms/risc-v/eic7700x/boards/starpro64/index.rst`:
Building and booting NuttX for StarPro64
Signed-off-by: Lup Yuen Lee <luppy@appkaki.com>
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