scsi: ufs: bsg: Let result in struct ufs_bsg_reply be signed int

According to the comments in struct ufs_bsg_reply and its usage, the result
should be signed int, not __u32.

Signed-off-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>