- line was truncated because 64 characters were not sufficient
- length passed to snprintf should be full buffer length, not -1
- make the width of lock name field fixed
- fix alignment of lock type column
`uart_ll_get_txfifo_len` returns the number of bytes available in the
TX FIFO; The condition we need is "FIFO empty", not "FIFO has free
space". `uart_ll_is_tx_idle` does that, and also ensures that the last
character popped from the TX FIFO has been fully transmitted.
