Bluetooth: Controller: Remove unused members from llcp_df_rsp_cfg

ant_sw_len and ant_ids members of the structure llcp_df_rsp_cfg
were not used. These data are stored in lll_df_conn_tx_cfg
that is member of lll_conn. Unused members are removed.

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