comedi: vmk80xx: fix expression for tx buffer size
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v4.19.249 by commit 8b65a17d21412bd20e04d110b0e4bfed1ff0cb80, it was introduced in version v4.19.217 by commit 7a2021b896de1ad559d33b5c5cdd20b982242088. For more details please see the references link.