NFS: Fix more NFS debug related build warnings

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/fscache.c b/fs/nfs/fscache.c
index 419119c..ae65c16 100644
--- a/fs/nfs/fscache.c
+++ b/fs/nfs/fscache.c
@@ -327,7 +327,7 @@
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
 	struct nfs_server *nfss = NFS_SERVER(inode);
-	struct fscache_cookie *old = nfsi->fscache;
+	NFS_IFDEBUG(struct fscache_cookie *old = nfsi->fscache);
 
 	nfs_fscache_inode_lock(inode);
 	if (nfsi->fscache) {