scsi: core: scsi_host_cmd_pool is declared twice

struct scsi_host_cmd_pool has already been declared. Remove the duplicate.

Link: https://lore.kernel.org/r/20210325064632.855002-1-wanjiabing@vivo.comSigned-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

include/scsi/scsi_host.h

@@ -19,7 +19,6 @@ struct scsi_device;
 struct scsi_host_cmd_pool;
 struct scsi_target;
 struct Scsi_Host;
-struct scsi_host_cmd_pool;
 struct scsi_transport_template;