isofs: fix build regression

The new isofs_show_options() function fails to build when CONFIG_NLS
is disabled:

fs/isofs/inode.c: In function 'isofs_show_options':
fs/isofs/inode.c:518:44: error: 'CONFIG_NLS_DEFAULT' undeclared (first use in this function)
fs/isofs/inode.c:518:44: note: each undeclared identifier is reported only once for each function it appears in

This adds a check for CONFIG_JOLIET (which selects NLS), matching
the other uses of the iocharset handling in this file.

Fixes: 6fecb86a44f5 ("isofs: Implement show_options")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/isofs/inode.c

@@ -514,9 +514,11 @@ static int isofs_show_options(struct seq_file *m, struct dentry *root)
 	if (sbi->s_fmode != ISOFS_INVALID_MODE)
 		seq_printf(m, ",fmode=%o", sbi->s_fmode);
 
+#ifdef CONFIG_JOLIET
 	if (sbi->s_nls_iocharset &&
 	    strcmp(sbi->s_nls_iocharset->charset, CONFIG_NLS_DEFAULT) != 0)
 		seq_printf(m, ",iocharset=%s", sbi->s_nls_iocharset->charset);
+#endif
 	return 0;
 }