cciss: switch to using hlist for command list management

This both cleans up the code and also helps detect the spurious case
of a command attempted being removed from a queue it doesn't belong
to.

Acked-by: Mike Miller <mike.miller@hp.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/drivers/block/cciss_cmd.h b/drivers/block/cciss_cmd.h
index 43bf559..24e22de 100644
--- a/drivers/block/cciss_cmd.h
+++ b/drivers/block/cciss_cmd.h
@@ -265,8 +265,7 @@
   int			   ctlr;
   int			   cmd_type; 
   long			   cmdindex;
-  struct _CommandList_struct *prev;
-  struct _CommandList_struct *next;
+  struct hlist_node list;
   struct request *	   rq;
   struct completion *waiting;
   int	 retry_count;