extmod/vfs: Raise OSError(ENODEV) if mounting bdev without a filesystem.
extmod/vfs: Raise OSError(ENODEV) if mounting bdev without a filesystem.

This commit prevents uos.mount() from raising an AttributeError.
vfs_autodetect() is supposed to return an object that has a "mount" method,
so if no filesystem is found it should raise an OSError(ENODEV) and not
return the bdev itself which has no "mount" method.

adafruit/circuitpython,bvernoux/micropython,henriknelson/micropython,bvernoux/micropython,adafruit/circuitpython,adafruit/circuitpython,henriknelson/micropython,adafruit/circuitpython,bvernoux/micropython,henriknelson/micropython,henriknelson/micropython,henriknelson/micropython,bvernoux/micropython,bvernoux/micropython,adafruit/circuitpython,adafruit/circuitpython