As reported by Dan Carpenter this function causes a Sparse warning and
shouldn't be declared inline:

include/net/bluetooth/l2cap.h:837:30 error: marked inline, but without a
definition"

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>