RDMA/ucma: Support querying when IB paths are not reversible

The current query_route call can return up to two path records.  The
assumption being that one is the primary path, with optional support
for an alternate path.  In both cases, the paths are assumed to be
reversible and are used to send CM MADs.

With the ability to manually set IB path data, the rdma cm can
eventually be capable of using up to 6 paths per connection:

	forward primary, reverse primary,
	forward alternate, reverse alternate,
	reversible primary path for CM MADs
	reversible alternate path for CM MADs.

(It is unclear at this time if IB routing will complicate this)  In
order to handle more flexible routing topologies, add a new command to
report any number of paths.

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