rds: fix iband RDMA dependencies

Fix RDS Infiniband dependencies for RDMA so that these
build errors won't happen:

ERROR: "rdma_accept" [net/rds/rds.ko] undefined!
ERROR: "rdma_destroy_id" [net/rds/rds.ko] undefined!
ERROR: "rdma_connect" [net/rds/rds.ko] undefined!
ERROR: "rdma_destroy_qp" [net/rds/rds.ko] undefined!
ERROR: "rdma_listen" [net/rds/rds.ko] undefined!
ERROR: "rdma_notify" [net/rds/rds.ko] undefined!
ERROR: "rdma_create_id" [net/rds/rds.ko] undefined!
ERROR: "rdma_create_qp" [net/rds/rds.ko] undefined!
ERROR: "rdma_bind_addr" [net/rds/rds.ko] undefined!
ERROR: "rdma_resolve_route" [net/rds/rds.ko] undefined!
ERROR: "rdma_disconnect" [net/rds/rds.ko] undefined!
ERROR: "rdma_reject" [net/rds/rds.ko] undefined!
ERROR: "rdma_resolve_addr" [net/rds/rds.ko] undefined!

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>