scsi: remove abuses of scsi_populate_tag

Unless we want to build a SPI tag message we should just check SCMD_TAGGED
instead of reverse engineering a tag type through the use of
scsi_populate_tag_msg.

Also rename the function to spi_populate_tag_msg, make it behave like the
other spi message helpers, and move it to the spi transport class.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Reviewed-by: Hannes Reinecke <hare@suse.de>

drivers/scsi/aic7xxx/aic79xx_osm.c

@@ -1619,15 +1619,6 @@ ahd_linux_run_command(struct ahd_softc *ahd, struct ahd_linux_device *dev,
 	}
 
 	if ((dev->flags & (AHD_DEV_Q_TAGGED|AHD_DEV_Q_BASIC)) != 0) {
-		int	msg_bytes;
-		uint8_t tag_msgs[2];
-
-		msg_bytes = scsi_populate_tag_msg(cmd, tag_msgs);
-		if (msg_bytes && tag_msgs[0] != MSG_SIMPLE_TASK) {
-			hscb->control |= tag_msgs[0];
-			if (tag_msgs[0] == MSG_ORDERED_TASK)
-				dev->commands_since_idle_or_otag = 0;
-		} else
 		if (dev->commands_since_idle_or_otag == AHD_OTAG_THRESH
 		 && (dev->flags & AHD_DEV_Q_TAGGED) != 0) {
 			hscb->control |= MSG_ORDERED_TASK;

drivers/scsi/aic7xxx/aic7xxx_osm.c

@@ -1501,15 +1501,7 @@ ahc_linux_run_command(struct ahc_softc *ahc, struct ahc_linux_device *dev,
 	}
 
 	if ((dev->flags & (AHC_DEV_Q_TAGGED|AHC_DEV_Q_BASIC)) != 0) {
-		int	msg_bytes;
-		uint8_t tag_msgs[2];
-		
-		msg_bytes = scsi_populate_tag_msg(cmd, tag_msgs);
-		if (msg_bytes && tag_msgs[0] != MSG_SIMPLE_TASK) {
-			hscb->control |= tag_msgs[0];
-			if (tag_msgs[0] == MSG_ORDERED_TASK)
-				dev->commands_since_idle_or_otag = 0;
-		} else if (dev->commands_since_idle_or_otag == AHC_OTAG_THRESH
+		if (dev->commands_since_idle_or_otag == AHC_OTAG_THRESH
 				&& (dev->flags & AHC_DEV_Q_TAGGED) != 0) {
 			hscb->control |= MSG_ORDERED_TASK;
 			dev->commands_since_idle_or_otag = 0;