Split allocation of MTT range from creation of MR.  This will be useful for
implementing shared memory regions and userspace verbs.
Signed-off-by: NRoland Dreier <roland@topspin.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>