Revert "Port fix: Reinitialize serial buffer on every read to avoid concurrent rewrite"

[rsora]

Reverts #486 due to Create Serial Monitor missing output for high serial write frequency on Arduino Uno

[facchinm]

Ehm, why? Can you add a reference to some issue/report?

[rsora]

@facchinm as (maybe not so clearly, I admit it 😸 ) reported in the PR description, @smellai discovered that the buffer re-initialize fix exposed another bug that happens when a board like the Uno interacts with the create serial monitor.
The bug makes thech buffer grows indefinitely (or at least this is what we read from the logs) without generating encoded data (that causes the serial monitor UI get stuck on the create frontend).
We chose to revert the fix (since the Uno is the Create most used board) and start a more focused refactoring on the func (p *serport) reader() function internals.