Bluetooth: Controller: Fix missing conn update ind PDU validation

Fix missing validation of Connection Update Ind PDU. Ignore
invalid connection update parameters and force a silent
local connection termination.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>
(cherry picked from commit 4b6d3f1e)
Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>