Bluetooth: Remove unneeded locking

This patch removes unneeded locking in hci_le_adv_report_evt. There
is no need to lock hdev before calling mgmt_device_found.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>