RFC: drivers: serial: Use microseconds to represent timeout in asynchronous API

Chruściński, Krzysztof


there is an open PR with change UART Asynchronous API to use microseconds to represent timeouts in uart_tx() and uart_rx_enable() functions (currently milliseconds are used). Note that UART Asynchronous API is marked as unstable.

Note that when it's merged, code will compile but provided argument will be interpreted differently by the driver! Action is required on the user side to multiply previously provided argument by 1000 to get the same behavior.