Bluetooth: Remove unnecessary checks for auto-connected devices

If a device is in the pend_le_conns list it cannot at the same time also
have the need to be notified through mgmt_device_found. By making
check_pending_le_conn return whether it found an entry or not we can
avoid unnecessary checks in process_adv_report().

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