We add multiple dumps for debugfs, but only allocate memory this time and
only dump #0.

Link: https://lore.kernel.org/r/1571926105-74636-15-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>