scsi: lpfc: remove useless code in lpfc_sli4_bsg_link_diag_test

Remove variable assignments. The value stored in local variable _rc_ is
overwritten at line 2448:rc = lpfc_sli4_bsg_set_link_diag_state(phba,
0); before it can be used.

Addresses-Coverity-ID: 1226935
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>