Bluetooth: controller: Fix pointless expression

Seems due to incorrect rebase in commit 07270e52
("Bluetooth: controller: Coding style and refactoring"),
commit 95d55a2b ("Bluetooth: controller: Do not skip
one-shot tickers with slot"), and
commit 4ba2bb0d ("Bluetooth: controller: Be fair when
pre-empting a ticker"), a pointless expression was
introduced, fixed it.

Coverity-CID: 171563

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