gru: fix automatic retry of gru instruction failures

Fix bug in automatic retry of GRU instruction failures.  CBR substatus
(message queue failure) was being checked incorrectly.

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>