universal7580: Create root folders outside of vendor init script

universal7580: Create root folders outside of vendor init script

 * The core SELinux policies for vendor_init are being restricted as to
   comply with Treble. Simply adding a local rule to allow creating
   folders under rootfs would be enough, but at the same time defining
   the extra root folders and making use of AID/fs configuration file
   to set perms is more neat and clean.

 * Furthermore, with System As Root / is a read-only filesystem
   so we can't create our mountpoints from init script anymore

Change-Id: Idabd7ae72e4c4fd9daac5ba3be3e6236f79f251b