CVE-2026-72006 net/mlx5: free mlx5_st_idx_data on final dealloc

In the Linux kernel, the following vulnerability has been resolved: net/mlx5: free mlx5stidxdata on final dealloc Workloads that repeatedly allocate and release mkeys carrying TPH steering-tag hints e.g. churning RDMA MRs leak one struct mlx5stidxdata per cycle; kmemleak flags it as unreferenced...