drm/xe: free madvise VMA array on L2 flush failure

In the Linux kernel, the following vulnerability has been resolved: drm/xe: free madvise VMA array on L2 flush failure xe_vm_madvise_ioctl() allocates madvise_range.vmas in get_vmas(). After get_vmas() succeeds with at least one VMA, error paths must go through free_vmas so the array is released before the madvise details are destroyed. The L2 flush validation path added for PAT madvise rejects some SVM/userptr ranges after get_vmas() has succeeded, but jumps directly to madv_fini. This skips kfree(madvise_range.vmas), leaking the VMA array on each failed ioctl. Jump to free_vmas instead, matching the other validation failure paths after get_vmas() has succeeded. (cherry picked from commit c3a1c3579b1250060da73507a4acef712974c78a)