after sending the byte we wait until we receive the busmaster response.
sending the BRK is done in loopback mode.
Only caveat: we will get a phantom \0 in Rx FIFO
- fix typo - replace emsaurt_tx_poll by emsuart_tx_poll
- smart tx - enabled by EMS_Sys_Status.emsTxDelay == 2
use loopback to send in burst mode
- change emsuart_tx_poll to use emsuart_tx_buffer
- encapsulate uart_swap in #ifndef NO_UART_SWAP (private use)