block: move internal_tag to same cache line as tag

Since we removed cmd_type, we now have a hole in the struct. Move
the internal_tag member to the same cacheline as tag, since we
use them at the same time.

This doesn't fix the hole, just moves it elsewhere.
Signed-off-by: Jens Axboe <axboe@fb.com>

include/linux/blkdev.h

@@ -138,6 +138,9 @@ struct request {
 	int cpu;
 	unsigned int cmd_flags;		/* op and common flags */
 	req_flags_t rq_flags;
+
+	int internal_tag;
+
 	unsigned long atomic_flags;
 
 	/* the following two fields are internal, NEVER access directly */
@@ -209,8 +212,6 @@ struct request {
 
 	unsigned short ioprio;
 
-	int internal_tag;
-
 	void *special;		/* opaque pointer available for LLD use */
 
 	int errors;