scsi: ufs: delete unused structure filed tr

Delete unused structure field tr in structure utp_upiu_req, since no person
uses it for task management.

Fixes: df032bf2 ("scsi: ufs: Add a bsg endpoint that supports UPIUs")
Link: https://lore.kernel.org/r/20191205220912.5696-1-huobean@gmail.com


Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>