KVM common MMU changes for 6.9:

  - Harden KVM against underflowing the active mmu_notifier invalidation
    count, so that "bad" invalidations (usually due to bugs elsehwere in the
    kernel) are detected earlier and are less likely to hang the kernel.

  - Fix a benign bug in __kvm_mmu_topup_memory_cache() where the object size
    and number of objects parameters to kvmalloc_array() were swapped.