dts: arm: nordic: nRF5340 add radio peripheral with DFE antenna config

Add radio peripheral to nrf5340_cpunet DTS. The peripheral
description includes antenna matrix congiuration for Direction
Finding extennsion.

Appropriate binding file for nRF radio peripheral already egxists.

There is no default antenna matrix configuration. Antennas number
and GPIOS mapping to DFEGPIOS is project specific.
Complete configuration must be provided by end user as overaly.

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