NFSD: Initialize pointer ni with NULL and not plain integer 0

Pointer ni is being initialized with plain integer zero. Fix
this by initializing with NULL.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4proc.c

@@ -1178,7 +1178,7 @@ extern void nfs_sb_deactive(struct super_block *sb);
 static __be32 nfsd4_ssc_setup_dul(struct nfsd_net *nn, char *ipaddr,
 		struct nfsd4_ssc_umount_item **retwork, struct vfsmount **ss_mnt)
 {
-	struct nfsd4_ssc_umount_item *ni = 0;
+	struct nfsd4_ssc_umount_item *ni = NULL;
 	struct nfsd4_ssc_umount_item *work = NULL;
 	struct nfsd4_ssc_umount_item *tmp;
 	DEFINE_WAIT(wait);

fs/nfsd/nfs4state.c

@@ -5531,7 +5531,7 @@ static void nfsd4_ssc_shutdown_umount(struct nfsd_net *nn)
 static void nfsd4_ssc_expire_umount(struct nfsd_net *nn)
 {
 	bool do_wakeup = false;
-	struct nfsd4_ssc_umount_item *ni = 0;
+	struct nfsd4_ssc_umount_item *ni = NULL;
 	struct nfsd4_ssc_umount_item *tmp;
 
 	spin_lock(&nn->nfsd_ssc_lock);