NFSv4: Convert nfs_alloc_seqid() to return an ERR_PTR() if allocation fails

When we relax the sequencing on the NFSv4.1 OPEN/CLOSE code, we will want
to use the value NULL to indicate that no sequencing is needed.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 5194933..b922e43 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -1003,11 +1003,11 @@
 	struct nfs_seqid *new;
 
 	new = kmalloc(sizeof(*new), gfp_mask);
-	if (new != NULL) {
-		new->sequence = counter;
-		INIT_LIST_HEAD(&new->list);
-		new->task = NULL;
-	}
+	if (new == NULL)
+		return ERR_PTR(-ENOMEM);
+	new->sequence = counter;
+	INIT_LIST_HEAD(&new->list);
+	new->task = NULL;
 	return new;
 }