Bluetooth: Controller: Fix scanner window close by using lll_disable

Fix race condition in setting up ISR callback and parameter
caused between ULL_HIGH and LLL context. As LLL IRQ is not
disabled the parameter and ISR callback would get out of
sync causing incorrect parameter supplied to callback and
hence leading to development assert in ull_scan_done().

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