rdma: replace deprecated ifconfig in doc

The ifconfig command has been deprecated for many years.
To encourage new users not to continue using it and learning
iproute2; the ifconfig should not be used in examples.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

Documentation/filesystems/nfs/nfs-rdma.txt

@@ -187,8 +187,10 @@ Check RDMA and NFS Setup
     To further test the InfiniBand software stack, use IPoIB (this
     assumes you have two IB hosts named host1 and host2):
 
-    host1$ ifconfig ib0 a.b.c.x
-    host2$ ifconfig ib0 a.b.c.y
+    host1$ ip link set dev ib0 up
+    host1$ ip address add dev ib0 a.b.c.x
+    host2$ ip link set dev ib0 up
+    host2$ ip address add dev ib0 a.b.c.y
     host1$ ping a.b.c.y
     host2$ ping a.b.c.x
 
@@ -229,7 +231,8 @@ NFS/RDMA Setup
 
     $ modprobe ib_mthca
     $ modprobe ib_ipoib
-    $ ifconfig ib0 a.b.c.d
+    $ ip li set dev ib0 up
+    $ ip addr add dev ib0 a.b.c.d
 
     NOTE: use unique addresses for the client and server