sunrpc: suppress warnings for unused procfs functions

There is a warning about unused variables when building with W=1 and no procfs:

net/sunrpc/cache.c:1660:30: error: 'cache_flush_proc_ops' defined but not used [-Werror=unused-const-variable=]
 1660 | static const struct proc_ops cache_flush_proc_ops = {
      |                              ^~~~~~~~~~~~~~~~~~~~
net/sunrpc/cache.c:1622:30: error: 'content_proc_ops' defined but not used [-Werror=unused-const-variable=]
 1622 | static const struct proc_ops content_proc_ops = {
      |                              ^~~~~~~~~~~~~~~~
net/sunrpc/cache.c:1598:30: error: 'cache_channel_proc_ops' defined but not used [-Werror=unused-const-variable=]
 1598 | static const struct proc_ops cache_channel_proc_ops = {
      |                              ^~~~~~~~~~~~~~~~~~~~~~

These are used inside of an #ifdef, so replacing that with an
IS_ENABLED() check lets the compiler see how they are used while
still dropping them during dead code elimination.

Fixes: dbf847e ("knfsd: allow cache_register to return error on failure")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

Author: arndb

net/sunrpc/cache.c

@@ -1674,12 +1674,14 @@ static void remove_cache_proc_entries(struct cache_detail *cd)
 	}
 }
 
-#ifdef CONFIG_PROC_FS
 static int create_cache_proc_entries(struct cache_detail *cd, struct net *net)
 {
 	struct proc_dir_entry *p;
 	struct sunrpc_net *sn;
 
+	if (!IS_ENABLED(CONFIG_PROC_FS))
+		return 0;
+
 	sn = net_generic(net, sunrpc_net_id);
 	cd->procfs = proc_mkdir(cd->name, sn->proc_net_rpc);
 	if (cd->procfs == NULL)
@@ -1707,12 +1709,6 @@ static int create_cache_proc_entries(struct cache_detail *cd, struct net *net)
 	remove_cache_proc_entries(cd);
 	return -ENOMEM;
 }
-#else /* CONFIG_PROC_FS */
-static int create_cache_proc_entries(struct cache_detail *cd, struct net *net)
-{
-	return 0;
-}
-#endif
 
 void __init cache_initialize(void)
 {