Bluetooth: mgmt: Allow local name changes while powered off

This patch makes it possible to set the local name before powering on
the device. The name will be applied using the hci_write_local_name
command once the device gets powered on.

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