RDMA/iser: struct iscsi_iser_task is declared twice

struct iscsi_iser_task has been declared at 201st line. Remove the
duplicate.

Link: https://lore.kernel.org/r/20210326113347.903976-1-wanjiabing@vivo.comSigned-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/iser/iscsi_iser.h

@@ -297,7 +297,6 @@ struct iser_login_desc {
 
 struct iser_conn;
 struct ib_conn;
-struct iscsi_iser_task;
 
 /**
  * struct iser_device - iSER device handle