SUNRPC: Update help Kconfig text

Clean up: refresh the help text for Kconfig items related to the sunrpc
module.  Remove obsolete URLs, and make the language consistent among
the options.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/Kconfig

@@ -1757,15 +1757,32 @@ config SUNRPC_XPRT_RDMA
 	tristate
 	depends on SUNRPC && INFINIBAND && EXPERIMENTAL
 	default SUNRPC && INFINIBAND
+	help
+	  This option enables an RPC client transport capability that
+	  allows the NFS client to mount servers via an RDMA-enabled
+	  transport.
+
+	  To compile RPC client RDMA transport support as a module,
+	  choose M here: the module will be called xprtrdma.
+
+	  If unsure, say N.
 
 config SUNRPC_BIND34
 	bool "Support for rpcbind versions 3 & 4 (EXPERIMENTAL)"
 	depends on SUNRPC && EXPERIMENTAL
 	help
-	  Provides kernel support for querying rpcbind servers via versions 3
-	  and 4 of the rpcbind protocol.  The kernel automatically falls back
-	  to version 2 if a remote rpcbind service does not support versions
-	  3 or 4.
+	  RPC requests over IPv6 networks require support for larger
+	  addresses when performing an RPC bind.  Sun added support for
+	  IPv6 addressing by creating two new versions of the rpcbind
+	  protocol (RFC 1833).
+
+	  This option enables support in the kernel RPC client for
+	  querying rpcbind servers via versions 3 and 4 of the rpcbind
+	  protocol.  The kernel automatically falls back to version 2
+	  if a remote rpcbind service does not support versions 3 or 4.
+	  By themselves, these new versions do not provide support for
+	  RPC over IPv6, but the new protocol versions are necessary to
+	  support it.
 
 	  If unsure, say N to get traditional behavior (version 2 rpcbind
 	  requests only).
@@ -1779,12 +1796,13 @@ config RPCSEC_GSS_KRB5
 	select CRYPTO_DES
 	select CRYPTO_CBC
 	help
-	  Provides for secure RPC calls by means of a gss-api
-	  mechanism based on Kerberos V5. This is required for
-	  NFSv4.
+	  Choose Y here to enable Secure RPC using the Kerberos version 5
+	  GSS-API mechanism (RFC 1964).
 
-	  Note: Requires an auxiliary userspace daemon which may be found on
-		http://www.citi.umich.edu/projects/nfsv4/
+	  Secure RPC calls with Kerberos require an auxiliary user-space
+	  daemon which may be found in the Linux nfs-utils package
+	  available from http://linux-nfs.org/.  In addition, user-space
+	  Kerberos support should be installed.
 
 	  If unsure, say N.
 
@@ -1798,11 +1816,12 @@ config RPCSEC_GSS_SPKM3
 	select CRYPTO_CAST5
 	select CRYPTO_CBC
 	help
-	  Provides for secure RPC calls by means of a gss-api
-	  mechanism based on the SPKM3 public-key mechanism.
+	  Choose Y here to enable Secure RPC using the SPKM3 public key
+	  GSS-API mechansim (RFC 2025).
 
-	  Note: Requires an auxiliary userspace daemon which may be found on
-	  	http://www.citi.umich.edu/projects/nfsv4/
+	  Secure RPC calls with SPKM3 require an auxiliary userspace
+	  daemon which may be found in the Linux nfs-utils package
+	  available from http://linux-nfs.org/.
 
 	  If unsure, say N.