NFS: Convert nfs4_set_ds_client to EXPORT_SYMBOL_GPL

This is not part of an external ABI...

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 5452ada..19ea7d9 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -1463,7 +1463,7 @@
 	dprintk("<-- %s %p\n", __func__, clp);
 	return clp;
 }
-EXPORT_SYMBOL(nfs4_set_ds_client);
+EXPORT_SYMBOL_GPL(nfs4_set_ds_client);
 
 /*
  * Session has been established, and the client marked ready.