fs_driver.py: fix "Back" issue on VfsFat due to trailing slash

internal_filesystem/lib/mpos/fs_driver.py

@@ -79,6 +79,7 @@ def _fs_dir_open_cb(drv, path):
     #print(f"_fs_dir_open_cb for path '{path}'")
     try:
         import os # for ilistdir()
+        path = path.rstrip('/') # LittleFS handles trailing flashes fine, but vfs.VfsFat returns an [Errno 22] EINVAL
         return {'iterator' : os.ilistdir(path)}
     except Exception as e:
         print(f"_fs_dir_open_cb exception: {e}")