Bluetooth: Controller: ull: df: use new LLCP structus in conn CTE req

The implementation of the ll_df_set_conn_cte_req_enable function was
based on former implementation of LLCPs. The CTE request and response
control procedures are not implemented in former LLCPs framework.
The code has been updated to use data structues from refactored
implementation of LLCPs.

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