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>

fs/nfs/dns_resolve.c

@@ -10,6 +10,7 @@
 
 #include <linux/sunrpc/clnt.h>
 #include <linux/dns_resolver.h>
+#include "dns_resolve.h"
 
 ssize_t nfs_dns_resolve_name(struct net *net, char *name, size_t namelen,
 		struct sockaddr *sa, size_t salen)