RDMA/ucma: Allow user space to pass AF_IB into resolve

Allow user space applications to call resolve_addr using AF_IB.  To
support sockaddr_ib, we need to define a new structure capable of
handling the larger address size.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>