Bluetooth: controller: nRF: Revert use of ticker compat mode as default

Ticker is now fixed to avoid catch up of periodic timeout under
large ISR latencies.

Revert commit a749e28d ("Bluetooth: controller: split:
nRF: Use ticker compat mode as default").

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