Bluetooth: controller: Fix post DLE/PHY update event length

Fix the controller implementation to perform connection
event length reservation based on the completed Data Length
Update and/or PHY Update Procedure.

This fix with avoid states/roles from stepping on each
others event length. Connection would have supervision timed
out or have stalled data transmissions due to insufficient
reserved air time.

Relates to #15171.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>