gru: fix prefetch and speculation bugs

Fix several bugs related to prefetch, ordering & speculation:

	- GRU cch_allocate() instruction causes cacheable memory
	  to be created. Add a barriers to prevent speculation
	  from prefetching data before it exists.
	- Add memory barriers before cache-flush instructions to ensure
	  that previously stored data is included in the line flushed to memory.

Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/misc/sgi-gru/gru_instructions.h

@@ -325,6 +325,7 @@ static inline void gru_flush_cache(void *p)
 static inline void gru_start_instruction(struct gru_instruction *ins, int op32)
 {
 	gru_ordered_store_int(ins, op32);
+	mb();
 	gru_flush_cache(ins);
 }