Make Volantis devices encryptable

Volantis SurfaceFlinger holds open a file on data partition.
SurfaceFlinger is not running when we trigger_default_encryption
but if we start it before starting defaultcrypto it locks open
data, so we can't unmount it.

It will start anyway when main starts, so not starting it here
is safe - it will just cause a 1-2 second delay in the graphics
appearing.

Change-Id: Idd546a578e62a24f999367b1407b37ad0f00f3a2