Add some print at some places such as error info and cq of exception IO,
device found etc, and also adjust some log levels.

All this to assist debugging ability.
Signed-off-by: NXiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: NJohn Garry <john.garry@huawei.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>