Bluetooth: Fix missing check for FIPS security level

When checking whether a legacy link key provides at least HIGH security
level we also need to check for FIPS level which is one step above HIGH.
This patch fixes a missing check in the hci_link_key_request_evt()
function.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Cc: stable@vger.kernel.org