bugfix(UART): fixed two UART issues:
bugfix(UART): fixed two UART issues:

1. uart_wait_tx_done works incorrect when sending a byte of data.
2. uart_set_rx_timeout sets an incorrect rx timeout value when ref_tick is enabled

closes https://github.com/espressif/esp-idf/issues/3631

espressif/esp-idf,espressif/esp-idf,espressif/esp-idf,espressif/esp-idf