Staging: line6: remove teardown code from module_exit path

These pcm values should all be stopped properly when the device is
removed from the system (i.e. when disconnect is called), so there's no
need to duplicate this when the module is unloaded as well.

CC: Markus Grabner <grabner@icg.tugraz.at>
CC: Stefan Hajnoczi <stefanha@gmail.com>
CC: Julia Lawall <julia@diku.dk>
CC: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>