nvme: Makefile: remove dead build rule

Remove dead build rule for drivers/nvme/host/scsi.c which has been
removed by commit ("nvme: Remove SCSI translations").

Signed-off-by: Valentin Rothberg <vrothberg@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>