Bluetooth: EDTT: Remove ncmd and opcode from EDTT command response

Encode all types of EDTT command response with similar structure to how
it is generated from command complete when it is generated from the
command status.
This structure will be:
2 byte EDTT command response code
2 byte EDTT length field
1 byte HCI status
N bytes of command output parameters

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>