Minor corrections and additions to 'scsi_logging_level', as pointed out
by Chuck Ebbert.
Also point out the IBM S390-tools 'scsi_logging_level' script.
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>