bluetooth: controller: enable Coded PHY support for nRF52811

Nordic nRF52811 SoC has a 2.4GHx Radio which supports
LE Coded PHY, so we add the option to build a BLE
Controller for nRF52811 platforms with LE Coded PHY
support.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>