Fix inconsistent function signature in CDC.cpp

[echtzeit-dev]

USBAPI.h declares the return type of Serial_::baud() as uint32_t

This causes an error when building the framework with Clang, because it typedefs arm-none-eabi uint32_t to unsigned int and not to unsigned long like gcc-arm-none-eabi.

[CLAassistant]

All committers have signed the CLA.

[facchinm]

LGTM, thanks! If you could sign the CLA I'll be glad to merge it immediately 🙂

[echtzeit-dev]

I have 3 more fixes. They are rather small as well. Should I make separate PRs or would you prefer a single one with 3 commits?

[echtzeit-dev]

FYI: There appears to be lag in the CLA check. I signed it and the page behind link confirms that, but the check here is still pending (even after clicking the recheck link).

[per1234]

Hi @echtzeit-dev. I don't think it is a lag. The check is done against the user who created the commit. That is @weliveindetail, so it is @weliveindetail who must sign the CLA in order for the check to pass.

Hopefully the check will automatically pass once that has been done. If not, please comment here and we will investigate.

[weliveindetail]

Thanks for you note @per1234! It worked.

[echtzeit-dev]

FYI: There appears to be lag in the CLA check. I signed it and the page behind link confirms that, but the check here is still pending (even after clicking the recheck link).

I added them here directly: #136 (commits)

[echtzeit-dev]

@facchinm Are you still considering to merge this? Otherwise, do you have any questions or change requests? Thx