RDMA/cma: Add check to validate that cm_id is bound to a device

Several checks in the rdma_cm check against the state of the
cm_id, but only to validate that the cm_id is bound to an underlying
transport specific CM and an RDMA device.  Make the check explicit
in what we're trying to check for, since we're not synchronizing
against the cm_id state.

This will allow a user to disconnect a cm_id or reject a connection
after receiving a device removal event.

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