Update x/sys and x/net modules to support Risc-V

[carlosedp]

Updating projects using libraries that were recently updated to support Risc-V.

Go upstream work is tracked on: golang/go#27532

Risc-V software support tracker on https://github.com/carlosedp/riscv-bringup

[codecov]

Codecov Report

Merging #1344 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1344   +/-   ##
=======================================
  Coverage   84.39%   84.39%           
=======================================
  Files          27       27           
  Lines        2019     2019           
=======================================
  Hits         1704     1704           
  Misses        205      205           
  Partials      110      110

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