GRU Driver: /proc interfaces

This file externalizes some GRU state & statistics to the user using the
/proc file system.

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>