nfsd: define exports_proc_ops with CONFIG_PROC_FS

gcc with W=1 and ! CONFIG_PROC_FS
fs/nfsd/nfsctl.c:161:30: error: ‘exports_proc_ops’
  defined but not used [-Werror=unused-const-variable=]
  161 | static const struct proc_ops exports_proc_ops = {
      |                              ^~~~~~~~~~~~~~~~

The only use of exports_proc_ops is when CONFIG_PROC_FS
is defined, so its definition should be likewise conditional.
Signed-off-by: NTom Rix <trix@redhat.com>
Reviewed-by: NJeff Layton <jlayton@kernel.org>
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfsctl.c

@@ -153,18 +153,6 @@ static int exports_net_open(struct net *net, struct file *file)
 	return 0;
 }
 
-static int exports_proc_open(struct inode *inode, struct file *file)
-{
-	return exports_net_open(current->nsproxy->net_ns, file);
-}
-
-static const struct proc_ops exports_proc_ops = {
-	.proc_open	= exports_proc_open,
-	.proc_read	= seq_read,
-	.proc_lseek	= seq_lseek,
-	.proc_release	= seq_release,
-};
-
 static int exports_nfsd_open(struct inode *inode, struct file *file)
 {
 	return exports_net_open(inode->i_sb->s_fs_info, file);
@@ -1458,6 +1446,19 @@ static struct file_system_type nfsd_fs_type = {
 MODULE_ALIAS_FS("nfsd");
 
 #ifdef CONFIG_PROC_FS
+
+static int exports_proc_open(struct inode *inode, struct file *file)
+{
+	return exports_net_open(current->nsproxy->net_ns, file);
+}
+
+static const struct proc_ops exports_proc_ops = {
+	.proc_open	= exports_proc_open,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= seq_release,
+};
+
 static int create_proc_exports_entry(void)
 {
 	struct proc_dir_entry *entry;