igmp: Fix data-races around sysctligmpllm_reports.
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 v5.4.208 by commit 1656ecaddf90e2a070ec2d2404cdae3edf80faca, it was introduced in version v4.3 by commit df2cf4a78e488d26728590cb3c6b4fe4c4862c77. For more details please see the references link.