scsi: scsi_transport_fc: Use scsi_cmd_to_rq() instead of scsi_cmnd.request

Prepare for removal of the request pointer by using scsi_cmd_to_rq()
instead. This patch does not change any functionality.

Link: https://lore.kernel.org/r/[e-mail]
Cc: Christoph Hellwig <[e-mail]>
Cc: Hannes Reinecke <[e-mail]>
Cc: Ming Lei <[e-mail]>
Reviewed-by: Hannes Reinecke <[e-mail]>
Signed-off-by: Bart Van Assche <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/scsi_transport_fc.c

···
 	struct fc_rport *rport = starget_to_rport(scsi_target(scmd->device));
 
 	if ((rport->port_state != FC_PORTSTATE_ONLINE) &&
-		(scmd->request->cmd_flags & REQ_FAILFAST_TRANSPORT)) {
+		(scsi_cmd_to_rq(scmd)->cmd_flags & REQ_FAILFAST_TRANSPORT)) {
 		set_host_byte(scmd, DID_TRANSPORT_MARGINAL);
 		return false;
 	}