fc: FCP_PTA_SIMPLE is 0

Not need to have an if/else to either assign FCP_PTA_SIMPLE or 0
to a variable.

Btw, it seems we really should factor generating a fcp cmnd from
a scsi_cmnd into a common helper.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>