Fix rounding in _ms_to_ticks()

[pizi-nordic]

At the moment the _ms_to_ticks() rounds down, which results in premature expiration of timeouts scheduled just before edge of tick. To fix that we have to revert #9745 in order to restore rounding up.

[pabigot]

That's one place where things get rounded down. The same truncation happens in z_clock_elapsed in multiple architectures where fractional ticks are discarded. Overall the need to traffic in durations that are downsampled from the hardware clock resolution in multiple places makes proper management of sleeps and alarms quite difficult.

[ioannisg]

@pizi-nordic @carlescufi is this still applicable, and if so, how can we address it ifor 2.0?

[pizi-nordic]

IMHO it should be fixed. I can prepare PR after I finish userspace logging.