NVMe: Fix for BLK_DEV_INTEGRITY not set

Need to define and use appropriate functions for when BLK_DEV_INTEGRITY
is not set.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>