target: remove control CDB flags

We don't need three flags to classifiy the CDB as we can check for a NULL S/G
list for a dataless command, and can infer from the absence of the data flag
that we deal with a control CDB.  Also remove the _SG_IO from the data CDB
flag as all I/O is dont on S/G lists now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/loopback/tcm_loop.c b/drivers/target/loopback/tcm_loop.c
index 38dfac2..f65dc9d 100644
--- a/drivers/target/loopback/tcm_loop.c
+++ b/drivers/target/loopback/tcm_loop.c
@@ -211,12 +211,11 @@
 	/*
 	 * Because some userspace code via scsi-generic do not memset their
 	 * associated read buffers, go ahead and do that here for type
-	 * SCF_SCSI_CONTROL_SG_IO_CDB.  Also note that this is currently
-	 * guaranteed to be a single SGL for SCF_SCSI_CONTROL_SG_IO_CDB
-	 * by target core in target_setup_cmd_from_cdb() ->
-	 * transport_generic_cmd_sequencer().
+	 * non-data CDBs.  Also note that this is currently guaranteed to be a
+	 * single SGL for this case by target core in
+	 * target_setup_cmd_from_cdb() -> transport_generic_cmd_sequencer().
 	 */
-	if (se_cmd->se_cmd_flags & SCF_SCSI_CONTROL_SG_IO_CDB &&
+	if (!(se_cmd->se_cmd_flags & SCF_SCSI_DATA_CDB) &&
 	    se_cmd->data_direction == DMA_FROM_DEVICE) {
 		struct scatterlist *sg = scsi_sglist(sc);
 		unsigned char *buf = kmap(sg_page(sg)) + sg->offset;