Create a file structure which was used to save the memory address and DQ
pointer for DQ at debugfs. This structure is bound to the corresponding
debugfs file, it can help callback function of debugfs file to get what it
need.

Link: https://lore.kernel.org/r/1571926105-74636-8-git-send-email-john.garry@huawei.comSigned-off-by: Luo Jiaxing <luojiaxing@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>