If the time driver now() is called before the syscounter is enabled on nrf54,
it would hang. The fix checks if syscounter is enabled, and returns 0
if not.

feat: add support for buffered write mode for rram

tiny improvements for nrf init code docs

nrf/cracen: fix bus fault on drop.

Accessing the RNGCONTROL reg bus faults when ENABLE.RNG=0.
Do all the enabling in start_rng/stop_rng, then do nothing on drop.

This is fine now that we only have blocking RNG, we'll have to do something fancier in the future.