Fix serial u8 register write

[dcz-self]

The & to *mut conversion failed the build.

Fixes #58

This follows advice to eliminate the & completely: #59 (comment) . Instead, there's only a conversion from *const to *mut.

[Disasm]

Thank you!

[Disasm]

CI is broken, but I fixed it in another PR and verified that this PR builds as expected.

[dcz-self]

Thank you for merging this.
Please let me know if there's anything I can do to help. I realize that maintenance takes a lot of time so I'd like to take a more active role than just to wait for a new release :P

[Disasm]

You can prepare the release instead of waiting for it :) You can also help with testing different PRs, and create new ones (I hope @rmsyn or someone from the RISC-V Team will be able to help with reviewing those).

[dcz-self]

Is there anything I need to know before the release? Bump versions numbers?
I'd like to include the hal 1.0 update, but I'm not sure if I should just merge it locally as part of the release MR, or through the Github UI.

[Disasm]

I suppose the release checklist is something like this:

• check changes since the last release to decide whether the next release is a patch or a minor release
• bump version numbers
• update CHANGELOG.md

The hal 1.0 update needs to be reviewed and tested I guess, and merge conflicts resolved.

[dcz-self]

I'll do that. The hal update may take me longer, because I just learned of an incoming deadline.

[rmsyn]

I hope @rmsyn or someone from the RISC-V Team will be able to help with reviewing those

Definitely! Feel free to ping me in any PR/issue you would like reviewed.