RDMA/ucma: Allow user space to bind to AF_IB

Support user space binding to addresses using AF_IB.  Since
sockaddr_ib is larger than sockaddr_in6, we need to define a larger
structure when binding using AF_IB.  This time we use sockaddr_storage
to cover future cases.

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