Update for Cosimulation (Parameter Overrides + Misc. Cleanup)

[abejgonzalez]

Related Issues/PRs: https://github.com/riscv-boom/riscv-boom/pull/415 https://github.com/abejgonzalez/dromajo/pull/1

Release Notes: This PR is all the changes that BOOM (boom-core.org) has done in order to cosimulate using Dromajo. Here is a high-level list of all the changes:

• Add .gitignore
• Cleanup *_cosim.* functions to be more consistent with other functions within the files
• Added bootrom override
• Added dtb override
• Added parameter to have bootrom and dtb be contiguous
• Added reset vector override
• Added MMIO range override
• Added PLIC base/size overrides
• Added CLINT base/size overrides
• Added parameter to add X extension to the misa (though it is not used (this aligns with Rocket-Chip))

Any recommendations/concerns are welcome!

[et-tommythorn]

That looks great. Let me comb it over tomorrow before merging. Thanks for the improvement.

[et-tommythorn]

Ok, I resolved conflicts, squashed, and pushed.

Next time, please make sure that it's rebased on the current master before submitting a request. Also, do squash all changes unless there a very good reason for individual commits. Finally, no merge commits, thanks.

[abejgonzalez]

Sorry about that, bad habit. Also, I didn't know what the strategy was for doing PRs (rebase or merge commit) so I left that alone for now. In any case, thanks for the review/feedback!

[et-tommythorn]

No problem; I was merely providing the requested feedback. The rebase vs. merges is largely an question of taste (good taste and bad taste :)