sgi-gru: add support to the GRU driver for message queue interrupts

Add support to the GRU driver for message queue interrupts.

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