verilog-indent-level-directive

verilog-indent-level-directive is a variable defined in `verilog-mode.el'.
Its value is

1

• This variable is safe as a file local variable if its value
  satisfies the predicate `integerp'.

Documentation:
Indentation to add to each level of `ifdef declarations.
Set to 0 to have all directives start at the left side of the screen.

You can customize this variable.