KVM: explicitly set rmap_head->val to 0 in pte_list_desc_remove_entry()

When we reach here, we have desc->sptes[j] = NULL with j = 0.
So we can replace desc->sptes[0] with 0 to make it more clear.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -1414,7 +1414,7 @@ pte_list_desc_remove_entry(struct kvm_rmap_head *rmap_head,
 	if (j != 0)
 		return;
 	if (!prev_desc && !desc->more)
-		rmap_head->val = (unsigned long)desc->sptes[0];
+		rmap_head->val = 0;
 	else
 		if (prev_desc)
 			prev_desc->more = desc->more;