Bluetooth: Fix checks for changes in connection parameters

Added checks for latency and timeout changes requested in
bt_conn_le_param_update, to decide if connection parameter
update is needed.

Change-id: I9de9f566158c5ade808ed356cb90b27186aa0243
Signed-off-by: Vinayak Chettimada <vinayak.kariappa.chettimada@nordicsemi.no>