Bluetooth: controller: split: Fix missing data len update event

Fix missing generation of data length update HCI event when
effective tx and rx timings change due to PHY update
procedure.

Fixes BT LL TS 5.1.0 test:
LL/CON/MAS/BV-52-C [Master Receiving Data, LE Coded, CI
Change]

Relates to #17097.

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