scsi: target: iscsi: Remove the iscsi_data_count structure

This patch removes the iscsi_data_count structure and the
iscsit_do_rx_data() function because they are used only by rx_data()

Link: https://lore.kernel.org/r/20200424113913.17237-1-mlombard@redhat.com


Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>