Bluetooth: Controller: df: CTE request not disabled if run in single shot mode

[ppryga-nordic]

Describe the bug
There is an error. CTE request control procedure can be run in single
shot or periodic mode. In case of run in single show, it is not disabled after completion.

The code responsible for the disable was deleted in commit: ac7d050.

To Reproduce
Steps to reproduce the behavior:

1. Build direction_finding_central sample.
2. Change

const struct bt_df_conn_cte_req_params cte_req_params = {
	.interval = CTE_REQ_INTERVAL,

to

const struct bt_df_conn_cte_req_params cte_req_params = {
	.interval = 0,

3. Add call to enable_cte_reqest in cte_recv_cb.
4. Observe console output. Second call to enable_cte_req will fail with error code.

Expected behavior
The second call to ebq_cte_req should be successful.

Impact
Prevents conformance tests to pass.
Use of single shot CTE request in production projects is not possible.