n80xx-common: fix fstab for vold managed volumes

although vold is working for in|external mounts
but it shows this error below:

E/DirectVolume( 1821): Vold managed volumes must have auto mount point; ignoring /storage/sdcard1
E/DirectVolume( 1821): Vold managed volumes must have auto mount point; ignoring /storage/usbdisk0

Signed-off-by: Humberto Borba <humberos@gmail.com>
Change-Id: Ia2c616850110ebc3c274d7dae33bfe1fd55b89a8