nvme-pci: remove duplicate check

This is a cleanup patch doesn't change any functionality. It removes
the duplicate call to the blk_integrity_rq() in the nvme_map_data().

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>