scsi: pm80xx: remove redundant assignments to variable rc

There are several occasions where variable rc is being initialized with a
value that is never read and error is being re-assigned a little later on.
Clean up the code by removing rc entirely and just returning the return
value from the call to pm8001_issue_ssp_tmf

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>