block: Link backup into block core

Some programs that add a dependency on it will use
the block layer directly.
Signed-off-by: NWen Congyang <wency@cn.fujitsu.com>
Signed-off-by: NChanglong Xie <xiecl.fnst@cn.fujitsu.com>
Signed-off-by: NWang WeiWei <wangww.fnst@cn.fujitsu.com>
Signed-off-by: Nzhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NJeff Cody <jcody@redhat.com>
Message-id: 1469602913-20979-5-git-send-email-xiecl.fnst@cn.fujitsu.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/Makefile.objs

@@ -22,11 +22,11 @@ block-obj-$(CONFIG_ARCHIPELAGO) += archipelago.o
 block-obj-$(CONFIG_LIBSSH2) += ssh.o
 block-obj-y += accounting.o dirty-bitmap.o
 block-obj-y += write-threshold.o
+block-obj-y += backup.o
 
 block-obj-y += crypto.o
 
 common-obj-y += stream.o
-common-obj-y += backup.o
 
 iscsi.o-cflags     := $(LIBISCSI_CFLAGS)
 iscsi.o-libs       := $(LIBISCSI_LIBS)