soc: arm: nordic: introduce Kconfig option for LE Coded PHY

We, now, have multiple nRF52x SoCs with 2.4GHz
Radio with LE Coded PHY Capabilities. Therefore,
we would like to have a Kconfig option and select
it in the corresponding SoCs. This allows us to
simplify several #ifdef blocks in the nRF Bluetooth
Controller that would, otherwise, require listing
all nRF SoCS with LE Coded PHY support.

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