UOS compatibility for mpremote compatibility

uos.py

import storage
from os import *

def get_mount_for(path):
    path = path.rstrip("/")
    if path[0] != "/":
        path = os.getcwd() + "/" + path
    while len(path) > 0:
        try:
            return storage.getmount(path)
        except OSError:
            pos = path.rfind("/")
            path = path[:pos]
    return None

def ilistdir(path):
    mount = get_mount_for(path)
    return mount.ilistdir(path)