rvgo: Fix inverted hint writing conditional check

[pcw109550]

Description

Fix hint writing logic at vm.go. Equal bug compared with ethereum-optimism/optimism#10514.

Tests

Mirrored unit test and fuzz test.

Ensured syscall instruction is 4 bytes written, for avoiding fuzz test failure.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.46%. Comparing base (0bbe1c1) to head (33afd26).

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #61      +/-   ##
==========================================
+ Coverage   70.39%   70.46%   +0.07%     
==========================================
  Files          19       19              
  Lines        2810     2810              
==========================================
+ Hits         1978     1980       +2     
+ Misses        743      742       -1     
+ Partials       89       88       -1     

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