sunrpc: Remove unused function ip_map_lookup

Fix the following clang warnings:

net/sunrpc/svcauth_unix.c:306:30: warning: unused function
'ip_map_lookup' [-Wunused-function].
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

net/sunrpc/svcauth_unix.c

@@ -303,15 +303,6 @@ static struct ip_map *__ip_map_lookup(struct cache_detail *cd, char *class,
 		return NULL;
 }
 
-static inline struct ip_map *ip_map_lookup(struct net *net, char *class,
-		struct in6_addr *addr)
-{
-	struct sunrpc_net *sn;
-
-	sn = net_generic(net, sunrpc_net_id);
-	return __ip_map_lookup(sn->ip_map_cache, class, addr);
-}
-
 static int __ip_map_update(struct cache_detail *cd, struct ip_map *ipm,
 		struct unix_domain *udom, time64_t expiry)
 {