verilog: support ifdef in enum

[hirooih]

This is a fix to support the following coding style.

typedef enum logic {
    aaa,
    bbb
`ifdef bar
    ,ccc
`endif
} ifdef2_e;

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.89%. Comparing base (45735bd) to head (c407c42).
Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4140   +/-   ##
=======================================
  Coverage   85.89%   85.89%           
=======================================
  Files         239      239           
  Lines       58695    58696    +1     
=======================================
+ Hits        50416    50417    +1     
  Misses       8279     8279           

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