Linter fixes

[LucaRufer]

Fix multiple issues identified by a linter:

• Flipflop signal is assigned multiple times in an always construct for sequential circuits
• Shift expressions that might cause overflows

This PR has no functional changes.

[colluca]

Thanks for the contribution @LucaRufer!

In general this looks good to me, however it would be desirable to include the linter in the CI, if possible, to ensure that we don't have regressions from this point of view in the future.

Are you using an open source linter, or a proprietary one that we have access to at IIS?

[LucaRufer]

Hello @colluca, thank you for reviewing the PR.

We use Synopsys Spyglass as a Linter and as far as I know, you also have access to this tool at IIS. Unfortunately I won't be able to update the CI for you to use Spyglass, as I don't have access to IIS-internal tools.

[colluca]

Hello @colluca, thank you for reviewing the PR.

We use Synopsys Spyglass as a Linter and as far as I know, you also have access to this tool at IIS. Unfortunately I won't be able to update the CI for you to use Spyglass, as I don't have access to IIS-internal tools.

I see. I could try to set this up, perhaps tomorrow, and come back to you. Do you still have Mattermost? If so maybe we can discuss this further there.

[LucaRufer]

Unfortunatly, I do not have access to any IIS-internal communication channels anymore. However, you can reach me on Github or via e-mail.