Allow CSRRS/C to read CLEN-wide values

[andresag01]

Fixes #92

[andresag01]

@PeterRugg: I tried this fix as proposed here.

[PeterRugg]

Thanks for sorting this! Looks good, and the text is a lot clearer than the previous text. Is it worth adding a note about no write happening, and thus no representable/sealed check happening, when the rs1 index is zero (as discussed in the issue)? It's surely the most sensible interpretation at the moment, but could be worth making it explicit?

[andresag01]

@tariqkurd-repo @PeterRugg : I've made an explicit note about the no-write on CSRRS/CSRRC when rs1=x0

[arichardson]

This LGTM. Would be nice to have a note on csrr but not necessarily required in this pr.

[arichardson]

This LGTM. Would be nice to have a note on csrr but not necessarily required in this pr.

@andresag01 just to clarify this, I'm happy for you to rebase-and-merge this now. The note can be added later.

[andresag01]

@Timmmm : Could you please review again and resolve the conversation if you are happy with the changes? Thanks!

[tariqkurd-repo]

any objections to merging this one? @arichardson maybe you can do the honours