bluetooth: controller: nrf5: Add IC-specific reset function

In order to address anomalies 102, 106 and 107 in nRF52, add a generic
hal_radio_reset() that does additional processing when required by a
particular IC or IC family. Implement the fix for the nRF52.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>