RDS: Modularize RDMA and TCP transports

Enable the building of transports as modules.

Also, improve consistency of Kconfig messages in relation to other
protocols, and move build dependency on IB from the RDS core code
to the rds_rdma module.

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

net/rds/Kconfig

@@ -1,14 +1,28 @@
 
 config RDS
-	tristate "Reliable Datagram Sockets (RDS) (EXPERIMENTAL)"
-	depends on INET && INFINIBAND_IPOIB && EXPERIMENTAL
-	depends on INFINIBAND && INFINIBAND_ADDR_TRANS
+	tristate "The RDS Protocol (EXPERIMENTAL)"
+	depends on INET && EXPERIMENTAL
 	---help---
-	  RDS provides reliable, sequenced delivery of datagrams
-	  over Infiniband.
+	  The RDS (Reliable Datagram Sockets) protocol provides reliable,
+	  sequenced delivery of datagrams over Infiniband, iWARP,
+	  or TCP.
+
+config RDS_RDMA
+	tristate "RDS over Infiniband and iWARP"
+	depends on RDS && INFINIBAND && INFINIBAND_ADDR_TRANS
+	---help---
+	  Allow RDS to use Infiniband and iWARP as a transport.
+	  This transport supports RDMA operations.
+
+config RDS_TCP
+	tristate "RDS over TCP"
+	depends on RDS
+	---help---
+	  Allow RDS to use TCP as a transport.
+	  This transport does not support RDMA operations.
 
 config RDS_DEBUG
-        bool "Debugging messages"
+        bool "RDS debugging messages"
 	depends on RDS
         default n