There was an inconsistency in the API as z_nrf_rtc_timer_chan_alloc
returned int but other function were using uint32_t for channel
argument. Updated api to use int32_t everywhere.
Update nrf_802154 driver which was using this api to use int32_t.
Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
Extended nrf_rtc_timer driver to expose API for using RTC for
other purposes. System timer is using one compare channels,
other channels may be used through this API.
Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>