KVM: Remove unused "rmap_overflow" variable

	unsigned int n_alloc_mmu_pages;

	struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];

	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];

	unsigned long rmap_overflow;

	struct list_head vm_list;

	struct file *filp;

	struct kvm_io_bus mmio_bus;