scsi: scsi_error: DID_SOFT_ERROR comment clean up

Updated comment. We are keeping track of maximum number of retries per
command via retries/allowed in struct scsi_cmnd. Corrected comment
positioning.

[mkp: applied by hand]

Signed-off-by: Petros Koutoupis <petros@petroskoutoupis.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>