kernel: Bluetooth: L2CAP: Fix use-after-free in l2cap_disconnect_{req,rsp}

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix use-after-free in l2capdisconnectreq,rsp Similar to commit d0be8347c623 "Bluetooth: L2CAP: Fix use-after-free caused by l2capchanput", just use l2capchanholdunlesszero to prevent referencing a channel that i...