nvme: rename apptag and appmask to lbat and lbatm

Rename apptag and appmask to lbat and lbatm so that it matches the field
names used in NVMe spec.

Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>