Bluetooth: Controller: Ticker low latency with lazy skip

Update the legacy low latency variant of the ticker
implementation to skip to next periodic interval when
ticks to expire is behind the current tick. This makes
the low latency variant of the implementation consistent
with the default ticker implementation.

Also, cleanup conditional compiles in the implementation.

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