RDMA/cma: Add support for AF_IB to rdma_resolve_addr()

Allow the user to specify the remote address using AF_IB format.  When
AF_IB is used, the remote address simply needs to be recorded, and no
resolution using ARP is done.  The local address may still need to be
matched with a local IB device.

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