Update vfs.c

Hide long filename support variables if LFN is not enabled

vfs.c

@@ -45,7 +45,9 @@ int vfs_read (void* buffer, int dummy, int len, vfs_file_t* file) {
 
 vfs_dirent_t* vfs_readdir(vfs_dir_t* dir) {
 	FILINFO fi;
+#if _USE_LFN
 	fi.lfname = NULL;
+#endif
 	FRESULT r = f_readdir(dir, &fi);
 	if (r != FR_OK) return NULL;
 	if (fi.fname[0] == 0) return NULL;
@@ -55,7 +57,9 @@ vfs_dirent_t* vfs_readdir(vfs_dir_t* dir) {
 
 int vfs_stat(vfs_t* vfs, const char* filename, vfs_stat_t* st) {
 	FILINFO f;
+#if _USE_LFN
 	f.lfname = NULL;
+#endif
 	if (FR_OK != f_stat(filename, &f)) {
 		return 1;
 	}