nanobsd: Fix typos

[jlduran]

Summary

Fix a number of typos in the code or comments.
Files under dhcpd, embedded, pcengines, and rescue were intentionally
omitted. These directories will be reviewed at a later date.

PR: 269884

[jlduran]

I guess these changes don't require a formal review, but just in case.

[zlei]

Looks good to me.

[imp]

Go ahead and commit this. While under mentorship, it's best to err on the side of asking, but once that's over, when you're doing other work in the area, like you are, spelling commits like this likely don't need review (though there's a tiny risk that your fixes might change the meaning, but that's rare).