Bluetooth: Controller: Fix incorrect drift comp on PHY update

Fix incorrect peripheral drift compensation when connection
events are overlapping and a PHY update causes the currently
used PHY to change.

Incorrect preamble to address that is calculated using
updated PHY was used causing supervision timeout.

Fixed by storing the PHY used in the current connection
event and using that for drift compensation calculation.

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