sepolicy: mount firmware partitions with firmware_file context

* we don't need to give ueventd and init_shell access across
  the entire vfat context

Change-Id: Ib65e1dbf46931f26350a3ffc8660971ecb03470e
dlx: re-enable performance profiles

Change-Id: Idac7fba0023167caf6fcd02b0120063a69528373