d2: stupid hack for selinux/rmt_storage

* we can't give rmt_storage access to kmem_device (neverallow ftL)
* rename it to rmt_storage2 (requires init change) and set policies
  on that while giving it rmt_placeholder
* omfg hax, don't try this at home

Change-Id: Ie959cf989a8141031f28f969a0c7e48a22d286a0