NFS: Fix a number of sparse warnings

Fix a number of "warning: symbol 'foo' was not declared. Should it be
static?" conditions.

Fix 2 cases of "warning: Using plain integer as NULL pointer"

fs/nfs/delegation.c:263:31: warning: restricted fmode_t degrades to integer
  - We want to allow upgrades to a WRITE delegation, but should otherwise
    consider servers that hand out duplicate delegations to be borken.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfs4filelayout.c b/fs/nfs/nfs4filelayout.c
index 716fac6..379a085 100644
--- a/fs/nfs/nfs4filelayout.c
+++ b/fs/nfs/nfs4filelayout.c
@@ -323,21 +323,21 @@
 	nfs_commitdata_release(wdata);
 }
 
-struct rpc_call_ops filelayout_read_call_ops = {
+static const struct rpc_call_ops filelayout_read_call_ops = {
 	.rpc_call_prepare = filelayout_read_prepare,
 	.rpc_call_done = filelayout_read_call_done,
 	.rpc_count_stats = filelayout_read_count_stats,
 	.rpc_release = filelayout_read_release,
 };
 
-struct rpc_call_ops filelayout_write_call_ops = {
+static const struct rpc_call_ops filelayout_write_call_ops = {
 	.rpc_call_prepare = filelayout_write_prepare,
 	.rpc_call_done = filelayout_write_call_done,
 	.rpc_count_stats = filelayout_write_count_stats,
 	.rpc_release = filelayout_write_release,
 };
 
-struct rpc_call_ops filelayout_commit_call_ops = {
+static const struct rpc_call_ops filelayout_commit_call_ops = {
 	.rpc_call_prepare = filelayout_write_prepare,
 	.rpc_call_done = filelayout_write_call_done,
 	.rpc_count_stats = filelayout_write_count_stats,
@@ -723,7 +723,7 @@
 	return (p_stripe == r_stripe);
 }
 
-void
+static void
 filelayout_pg_init_read(struct nfs_pageio_descriptor *pgio,
 			struct nfs_page *req)
 {
@@ -740,7 +740,7 @@
 		nfs_pageio_reset_read_mds(pgio);
 }
 
-void
+static void
 filelayout_pg_init_write(struct nfs_pageio_descriptor *pgio,
 			 struct nfs_page *req)
 {