Bluetooth: Fix broken usage of put_unaligned_le16

In case the struct is already __packed, there is no need to use
unaligned access to the data. So just use cpu_to_le16 or
__constant_cpu_to_le16 in these cases.

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