SUNRPC: sunrpc should not explicitly depend on NFS config options

Change explicit references to CONFIG_NFS_V4_1 to implicit ones
Get rid of the unnecessary defines in backchannel_rqst.c and
bc_svc.c: the Makefile takes care of those dependency.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 2b90292..3c6fe22 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1252,7 +1252,7 @@
 	}
 }
 
-#if defined(CONFIG_NFS_V4_1)
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
 /*
  * Process a backchannel RPC request that arrived over an existing
  * outbound connection
@@ -1301,7 +1301,7 @@
 	}
 }
 EXPORT_SYMBOL(bc_svc_process);
-#endif /* CONFIG_NFS_V4_1 */
+#endif /* CONFIG_SUNRPC_BACKCHANNEL */
 
 /*
  * Return (transport-specific) limit on the rpc payload.