Bluetooth: mgmt: Fix updating local name when powering on

When powering on we need to apply whatever name has been set through
mgmt_set_local_name. The appropriate place for this is mgmt_powered()
and not hci_setup() since this needs to be applied also if the HCI init
sequence was already completed but the adapter was still "powered off"
from a mgmt perspective due the the HCI_AUTO_OFF still being set.

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