Use supported features command to query what the connected device supports instead of relying on PCA board types

[thedjnK]

The DTM supported features command returns information about what the target device supports such as maximum packet length or PHYs. At present if connected to a device using the nordic SDK DTM code the PHY is set to 1M PHY by default but no other PHYs are listed even though the connected device (BL654/nRF52840) supports 2M PHY and LE coded PHYs because the code currently picks this information based upon the PCA board type.