Change type of result variables from int to ssize_t

[amxfonseca]

These variables are being used to store the result of read/write calls, which return a ssize_t value, which depending on platform can be bigger than an int.

We are not too concerned about an overflow, since usually we won't read/write that much data, but this clears out some compilation warnings.

[MCUdude]

@amxfonseca I see that content from this PR and #13 was recently added to git master, so this and #13 can be closed.
But is it you or @gsigh that has write access to this repo?

I'd really like to have #14 merged, since this is an obvious bug with a simple fix. However, we (the Avrdude team) have just discovered that libserialport are having problems with the CH340 and the FT231X on the latest macOS 14.3 version. We're still trying to figure out what's causing this and we have yet to test if #14 will fix the problem. See avrdudes/avrdude#1644 for details.

[amxfonseca]

Hi @MCUdude, I don't have write access, so it was definitely merged by @gsigh. I shall close the original PRs.

It would be nice if your PR also gets picked by some maintainer soon 🙏

[amxfonseca]

Merged 🎉

[MCUdude]

It would be nice if your PR also gets picked by some maintainer soon 🙏

Yes, I hope so. We just found out that the latest macOS version (14.3) has done some driver changes, and now the CH340 and the FTDI chips (FT232, FT231X etc.) don't work with libserialport either; with the same issue as the CP2102. #14 solves the problem though.