KVM: remove the unused declare

Remove it since it is not used anymore
Signed-off-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

include/linux/kvm_host.h

@@ -409,8 +409,6 @@ id_to_memslot(struct kvm_memslots *slots, int id)
 	return slot;
 }
 
-extern struct page *bad_page;
-
 int is_error_page(struct page *page);
 int kvm_is_error_hva(unsigned long addr);
 int kvm_set_memory_region(struct kvm *kvm,