Bluetooth: Fix checking for correct mgmt_load_link_keys parameters

The debug_keys parameter is only allowed to have the values 0x00 and
0x01. Any other value should result in a proper command status with
MGMT_STATUS_INVALID_PARAMS.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>