Bluetooth: trivial: Fix endian conversion mode

In L2CAP we use le16 format so change direction of conversion
from le16_to_cpu to cpu_to_le16.

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