[TASK] Adopt Smrnmi

[christian-herber-nxp]

Task Description

Current implementation of RNMIs is based on a custom Ibex implementation. When Smrnmi is ratified, move to the standard version.

Description of Done

Compliance to Smrnmi, custom solution removed

Associated PRs

No response

[MikeOpenHWGroup]

Removing original assignee as they are no longer assigned to this project.