CVE-2025-38032 mr: consolidate the ipmr_can_free_table() checks.

In the Linux kernel, the following vulnerability has been resolved: mr: consolidate the ipmrcanfreetable checks. Guoyu Yin reported a splat in the ipmr netns cleanup path: WARNING: CPU: 2 PID: 14564 at net/ipv4/ipmr.c:440 ipmrfreetable net/ipv4/ipmr.c:440 inline WARNING: CPU: 2 PID: 14564 at...