modules: hal_nordic: nrfx: cleanup

* Move all KConfig configuration from CMake to `nrfx_kconfig.h`
* Move macro utils from `nrfx_kconfig.h` to `nrfx_zephyr_utils.h`
* Move GRTC channels allocation from `nrfx_kconfig.h` to
  `nrfx_reserved_resources.h`

Signed-off-by: Marcin Szymczyk <marcin.szymczyk@nordicsemi.no>