scsi: uapi: ufs: Make utp_upiu_req visible to user space

in preparation to send UPIU requests via bsg.

Signed-off-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Bart Van Assche <Bart.VanAssche@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>