Bluetooth: Remove redundant IRK lookup in mgmt_device_found()

Now that we have the process_adv_report() function doing the IRK lookup
and updating the bdaddr we don't need to do this anymore in mgmt.c in
the mgmt_device_found() function.

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