Bluetooth: Controller: Add init CTE REQ and RSP variables on conn create

There were missing initialization for CTX request and response conotrol
procedure related variables. The variables were zeored on system
startup but not initialized when a connection is established.
In case of re-use of connection instance for new connection it was not
possible to setup procedures again.

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