linux-wandboard

USB: fix memory leak in cdc-acm

This fixes a memory leak on disconnect in cdc-acm

Thanks to 施金前 for finding it.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>