Bluetooth: Host: Update LE legacy pairing check

Updates the LE legacy pairing procedure as a result of errata ES-24491.
New part:
If the initiating device receives an LP_CONFIRM_R value that is equal to
the LP_CONFIRM_I value, the pairing process shall be aborted and fail
with "Confirm Value Failed" as reason.

Signed-off-by: Håvard Reierstad <haavard.reierstad@nordicsemi.no>