Bluetooth: mgmt: Use __constant when dealing with constants

__constant_cpu_to_le*() is the right go here.

Signed-off-by: Syam Sidhardhan <s.syam@samsung.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>