Using the RTC1 module for the LK tick (instead of arm systick)
Use the nrf_hal library for peripheral manipulation instead of
direct register access. Fixed race condition in current_time_hires
which would result in non monotonic readings.
Tested with clock_tests on:
nrf52-pca10040-test (nrf52832)
nrf52-pca10056-test (nrf52840)