The UART.IRQ_IDLE callback is called about two character times after the
last byte, or 1 ms, whichever is larger. For the irq, timer 0 is used.
machine_timer.c had to be reworked to make it's mechanisms available for
machine_uart.c.
The irq.flags() value is change only at a requested event. Otherwise keep
the state.
Signed-off-by: robert-hh <robert@hammelrath.com>
