bluetooth: controller: Use ticker must_expire to ensure ADV timing rand
bluetooth: controller: Use ticker must_expire to ensure ADV timing rand

Enabled use of ticker must_expire feature for ensuring ADV timing
randomization, even when ADV doesn't get air-time. This reduces ADV
collisions. Not active for nRF51 platform for now.

Signed-off-by: Morten Priess <eeac701aa7fa64292a00ac226283761853032460@oticon.com>

Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr