Add Return status to syscall for nvram

[kmeudic-ledger]

Description

This PR update syscall for nvram return status.

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• [ x] Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Tests
• Documentation
• Other (for changes that might not fit in any category)

Breaking changes

Return status code for one syscall.

Additional comments

Please post additional comments in this section if you have them, otherwise delete it.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 35.76%. Comparing base (44611f0) to head (53d681e).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #791   +/-   ##
=======================================
  Coverage   35.76%   35.76%           
=======================================
  Files          13       13           
  Lines        1591     1591           
=======================================
  Hits          569      569           
  Misses       1022     1022           

Flag	Coverage Δ
unittests	35.76% <ø> (ø)

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