scsi: lpfc: Fix Port going offline after multiple resets.

Observing lpfc port down after issuing hbacmd reset command

Failure in posting SGL buffers. If there is only one SGL buffer and rrq
is valid for its XRI, we are rightly returning NULL but not adding the
buffer back to the SGL list. So, number of buffers become less than
total count and repost fails during reset.

Add SGL buffer back to list before returning NULL.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>