[pmp] Use top-level straps for PMP reset values

[Razer6]

By using top-level straps for the PMP reset configuration its easier to implement different reset configurations if there are multiple Ibex cores in the system.

[GregAC]

I had intentionally avoid doing this with parameters when I first wrote it to avoid adding yet more parameters to Ibex, though given we've already got loads perhaps it doesn't matter.

Ultimately this is probably what we have to do but I'll have a think about alternative methods.

[GregAC]

@Razer6 we intend to take this, I just need to do a couple of checks to ensure there's no issues for non PMP configs or breakages in other things we don't check in CI I hope to get this done over the next couple of days.

[Razer6]

@GregAC No hurry on that one. We have changed that in our environment and are not dependent on vendoring in a new version of ibex at the moment.

[Razer6]

@GregAC @rswarbrick Could you take another look?

[GregAC]

@Razer6 yes will do

[Razer6]

Thanks @GregAC for the review. I just updated the changes for the nits.

[GregAC]

Thanks @Razer6