KVM: x86/mmu: remove unused variable

The last use of 'pfn' went away with the same-named argument to
host_pfn_mapping_level; now that the hugepage level is obtained
exclusively from the host page tables, kvm_mmu_zap_collapsible_spte
does not need to know host pfns at all.

Fixes: a8ac499b ("KVM: x86/mmu: Don't require refcounted "struct page" to create huge SPTEs")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -6416,13 +6416,11 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
 	u64 *sptep;
 	struct rmap_iterator iter;
 	int need_tlb_flush = 0;
-	kvm_pfn_t pfn;
 	struct kvm_mmu_page *sp;
 
 restart:
 	for_each_rmap_spte(rmap_head, &iter, sptep) {
 		sp = sptep_to_sp(sptep);
-		pfn = spte_to_pfn(*sptep);
 
 		/*
 		 * We cannot do huge page mapping for indirect shadow pages,