soc: nrf53: Add workaround for anomaly 160

Implement a workaround for the nRF53 anomaly 160. This consist of
a set of writes to certain hardware registers that is done at boot
and a piece of code that is executed when the CPU is made idle and
that prevents the CPU from switching between active and sleep modes
more than five times within a 200 us period.

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>