Fix svsim DPI function template

[uenoku]

This fixes two bugs in #4286

• VCS seems to be unhappy with initTestBenchScope; so replace it with initTestBenchScope();.
• getBitWidth exported DPI functions are used both for gettable/settable ports but Fix svsim to properly update svScope. Update DPISpec for firtool bump #4286 only added DPI decl for getter so this PR fixes by removing a filter.

Contributor Checklist

• Did you add Scaladoc to every public function/method?
• Did you add at least one test demonstrating the PR?
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• Bugfix

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[mwachs5]

is there a testcase we can add for this ?

[uenoku]

is there a testcase we can add for this ?

I tried but it looks tricky to reproduce the error in chisel repo. Internally we use svsim in a slightly different way and it looks there is no issue if we used chisel3.simulator directly.

[sequencer]

I tried but it looks tricky to reproduce the error in chisel repo. Internally we use svsim in a slightly different way and it looks there is no issue if we used chisel3.simulator directly.

Our team do provide the VCS infrastructure for rocket-chip and T1. Do we need to adopt it for chisel?

[uenoku]

Our team do provide the VCS infrastructure for rocket-chip and T1. Do we need to adopt it for chisel?

No I don't think so. It was not backend specific and internally we use some wrapper for svsim that manually constructs ModuleInfo .