Misc fixes

[msfschaffner]

This fixes a few things:

• Implement the nextdm register and add a signal input that can be used to input a (static) address.
• Correct behavior of the hartsel register so that it has WARL behavior as defined by the spec.
• Add an acknowledgement input for ndmreset. This is optional, and currently just wired to ndmreset_o in the top-level wrapper. It can however be used to implement more accurate reset completion tracking outside of rv_dm (e.g. the system reset manager).

CC @andreaskurth @a-will @gregAC

I will mark this as "ready for review" once I have integrated this into OpenTitan.

[msfschaffner]

Integrated into OT in https://github.com/lowRISC/opentitan/pull/22038