[SCSI] sym53c8xx: don't flood syslog with negotiation messages

sym53c8xx prints a negotiation message after every check condition.
This can add up to a lot of messages for removable-medium devices
(CD-ROM, tape drives, etc.) that are being polled, since they return
check condition when no medium is present.  This patch suppresses the
negotiation message if it would be the same as the last one printed.

Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>