ipv6/sit: use DEVSTATSINC() to avoid data-races
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 v5.15.86 by commit 222cc04356984f3f98acfa756a69d4bed7c501ac. For more details please see the references link.