chapters/io: Fix wwrite and rread logic from my-cat

[andrei811]

Prerequisite Checklist

• Read the contribution guidelines regarding submitting new changes to the project;
• Tested your changes against relevant architectures and platforms;
• Updated relevant documentation (if needed).

Description of changes

As per the read and write syscall wrappers, the functions return the number of bytes that have been successfully read or written. The buffer offset should be updated accordingly, as implemented.

[teodutu]

Thanks!

[teodutu]

To pass checkpatch [1] you'll have to reword your commits in a way similar to the previous ones in the repo [2]:

- chapters/io: Fix `rread()` and `wwrite()` logic
- chapters/io: Fix typo in `mmap_cp` task

Always use imperative verbs when making commits and prefix them with the component that you're changing. In addition, add a signed-off-by line to your commits and a short description of each of them. All these requirements are described here [3].

To reword your commits you'll have to run git rebase -i 30b256fd6e4dc20029a2e6503d938de9c7ed0564 (The latter ID is the sha of the last commit before yours; That's why it's easier to create a pull request from a different branch than main so that you can use git rebase -i main instead of a commit ID). This command will open your default editor with a 2-line list of your 2 commits. There you will change the first word of each line from "pick" to "r" (from "reword"), then save and exit. Then the editor will switch to the first and second commit messages that you can modify as I said above. After doing all this, use git push -f to push your changes to the remote repo.

[1] https://github.com/cs-pub-ro/operating-systems/actions/runs/12144710669/job/33893529314?pr=146#step:3:572
[2] https://github.com/cs-pub-ro/operating-systems/commits/main/
[3] https://github.com/cs-pub-ro/operating-systems/blob/main/CONTRIBUTING.md#commits