[SCSI] add failure return to scsi_init_shared_tag_map()

And use it in the stex driver.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/include/scsi/scsi_tcq.h b/include/scsi/scsi_tcq.h
index 4eea254b..d04d05a 100644
--- a/include/scsi/scsi_tcq.h
+++ b/include/scsi/scsi_tcq.h
@@ -138,9 +138,10 @@
  * @shost:	the host to share the tag map among all devices
  * @depth:	the total depth of the map
  */
-static inline void scsi_init_shared_tag_map(struct Scsi_Host *shost, int depth)
+static inline int scsi_init_shared_tag_map(struct Scsi_Host *shost, int depth)
 {
 	shost->bqt = blk_init_tags(depth);
+	return shost->bqt ? 0 : -ENOMEM;
 }
 
 #endif /* _SCSI_SCSI_TCQ_H */