Bluetooth: controller: Add Direction Finding specific KConfig

Add separated Kconfig file for Bluetooth 5.1 Direction Finding.
Enable controller support for:
 - transmission of CTE
 - 2us antenna switching
 - 1us antenna switching
if build for nRF52833 SOC.
Add HAS_HW_NRF_RADIO_BLE_DF to nrf52833 SOC configuration.

Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>