NFS: Fix up the declaration of nfs4_restart_rpc when NFSv4 not configured

Also rename it: it is used in generic code, and so should not have a 'nfs4'
prefix.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index d319bfb..db9b360 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -368,7 +368,7 @@
 	argp->offset += resp->count;
 	argp->pgbase += resp->count;
 	argp->count -= resp->count;
-	nfs4_restart_rpc(task, NFS_SERVER(data->inode)->nfs_client);
+	nfs_restart_rpc(task, NFS_SERVER(data->inode)->nfs_client);
 }
 
 /*